Bit-level inquiry and manipulation#
bge#
Name#
bge(3) - [BIT:COMPARE] Bitwise greater than or equal to
Synopsis#
result = bge(i,j)
elemental logical function bge(i, j)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: j
Characteristics#
a kind designated as ** may be any supported kind for the type
the integer kind of i and j may not necessarily be the same. In addition, values may be a BOZ constant with a value valid for the integer kind available with the most bits on the current platform.
The return value is of type default logical.
Description#
bge(3) Determines whether one integer is bitwise greater than or equal to another.
The bit-level representation of a value is platform dependent. The endian-ness of a system and whether the system uses a “two’s complement” representation of signs can affect the results, for example.
A BOZ constant (Binary, Octal, Hexadecimal) does not have a kind or type of its own, so be aware it is subject to truncation when transferred to an integer type. The most bits the constant may contain is limited by the most bits representable by any integer kind supported by the compilation.
Bit Sequence Comparison#
When bit sequences of unequal length are compared, the shorter sequence is padded with zero bits on the left to the same length as the longer sequence (up to the largest number of bits any available integer kind supports).
Bit sequences are compared from left to right, one bit at a time, until unequal bits are found or until all bits have been compared and found to be equal.
The bits are always evaluated in this order, not necessarily from MSB to LSB (most significant bit to least significant bit).
If unequal bits are found the sequence with zero in the unequal position is considered to be less than the sequence with one in the unequal position.
Options#
- i
The value to test if >= j based on the bit representation of the values.
- j
The value to test i against.
Result#
Returns .true. if i is bit-wise greater than j and .false. otherwise.
Examples#
Sample program:
program demo_bge
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: i
integer(kind=int8) :: byte
integer(kind=int8),allocatable :: arr1(:), arr2(:)
! BASIC USAGE
write(*,*)'bge(-127,127)=',bge( -127, 127 )
! on (very common) "two's complement" machines that are
! little-endian -127 will be greater than 127
! BOZ constants
! BOZ constants are subject to truncation, so make sure
! your values are valid for the integer kind being compared to
write(*,*)'bge(b"0001",2)=',bge( b"1", 2)
! ELEMENTAL
! an array and scalar
write(*, *)'compare array of values [-128, -0, +0, 127] to 127'
write(*, *)bge(int([-128, -0, +0, 127], kind=int8), 127_int8)
! two arrays
write(*, *)'compare two arrays'
arr1=int( [ -127, -0, +0, 127], kind=int8 )
arr2=int( [ 127, 0, 0, -127], kind=int8 )
write(*,*)'arr1=',arr1
write(*,*)'arr2=',arr2
write(*, *)'bge(arr1,arr2)=',bge( arr1, arr2 )
! SHOW TESTS AND BITS
! actually looking at the bit patterns should clarify what affect
! signs have ...
write(*,*)'Compare some one-byte values to 64.'
write(*,*)'Notice that the values are tested as bits not as integers'
write(*,*)'so the results are as if values are unsigned integers.'
do i=-128,127,32
byte=i
write(*,'(sp,i0.4,*(1x,1l,1x,b0.8))')i,bge(byte,64_int8),byte
enddo
! SIGNED ZERO
! are +0 and -0 the same on your platform? When comparing at the
! bit level this is important
write(*,'("plus zero=",b0)') +0
write(*,'("minus zero=",b0)') -0
end program demo_bge
Results:
How an integer value is represented at the bit level can vary. These are just the values expected on Today’s most common platforms …
> bge(-127,127)= T
> bge(b"0001",2)= F
> compare array of values [-128, -0, +0, 127] to 127
> T F F T
> compare two arrays
> arr1= -127 0 0 127
> arr2= 127 0 0 -127
> bge(arr1,arr2)= T T T F
> Compare some one-byte values to 64.
> Notice that the values are tested as bits not as integers
> so the results are as if values are unsigned integers.
> -0128 T 10000000
> -0096 T 10100000
> -0064 T 11000000
> -0032 T 11100000
> +0000 F 00000000
> +0032 F 00100000
> +0064 T 01000000
> +0096 T 01100000
> plus zero=0
> minus zero=0
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
bgt#
Name#
bgt(3) - [BIT:COMPARE] Bitwise greater than
Synopsis#
result = bgt(i, j)
elemental logical function bgt(i, j)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: j
Characteristics#
i is an integer or a boz-literal-constant.
j is an integer or a boz-literal-constant.
a kind designated as ** may be any supported kind for the type The integer kind of i and **j** may not necessarily be the same. kind. In addition, values may be a BOZ constant with a value valid for the integer kind available with the most bits on the current platform.
The return value is of type logical and of the default kind.
Description#
bgt determines whether an integer is bitwise greater than another. Bit-level representations of values are platform-dependent.
Options#
- i
reference value to compare against
- j
value to compare to i
Result#
The return value is of type logical and of the default kind. The result is true if the sequence of bits represented by i is greater than the sequence of bits represented by j, otherwise the result is false.
Bits are compared from right to left.
Examples#
Sample program:
program demo_bgt
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: i
integer(kind=int8) :: byte
! Compare some one-byte values to 64.
! Notice that the values are tested as bits not as integers
! so sign bits in the integer are treated just like any other
write(*,'(a)') 'we will compare other values to 64'
i=64
byte=i
write(*,'(sp,i0.4,*(1x,1l,1x,b0.8))')i,bgt(byte,64_int8),byte
write(*,'(a)') "comparing at the bit level, not as whole numbers."
write(*,'(a)') "so pay particular attention to the negative"
write(*,'(a)') "values on this two's complement platform ..."
do i=-128,127,32
byte=i
write(*,'(sp,i0.4,*(1x,1l,1x,b0.8))')i,bgt(byte,64_int8),byte
enddo
! see the BGE() description for an extended description
! of related information
end program demo_bgt
Results:
> we will compare other values to 64
> +0064 F 01000000
> comparing at the bit level, not as whole numbers.
> so pay particular attention to the negative
> values on this two's complement platform ...
> -0128 T 10000000
> -0096 T 10100000
> -0064 T 11000000
> -0032 T 11100000
> +0000 F 00000000
> +0032 F 00100000
> +0064 F 01000000
> +0096 T 01100000
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ble#
Name#
ble(3) - [BIT:COMPARE] Bitwise less than or equal to
Synopsis#
result = ble(i,j)
elemental logical function ble(i, j)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: j
Characteristics#
i and j may be of any supported integer kind, not necessarily the same. An exception is that values may be a BOZ constant with a value valid for the integer kind available with the most bits on the current platform.
the returned value is a logical scalar of default kind
Description#
ble(3) determines whether an integer is bitwise less than or equal to another, assuming any shorter value is padded on the left with zeros to the length of the longer value.
Options#
- i
the value to compare j to
- j
the value to be tested for being less than or equal to i
Result#
The return value is .true. if any bit in j is less than any bit in i starting with the rightmost bit and continuing tests leftward.
Examples#
Sample program:
program demo_ble
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: i
integer(kind=int8) :: byte
! Compare some one-byte values to 64.
! Notice that the values are tested as bits not as integers
! so sign bits in the integer are treated just like any other
do i=-128,127,32
byte=i
write(*,'(sp,i0.4,*(1x,1l,1x,b0.8))')i,ble(byte,64_int8),byte
write(*,'(sp,i0.4,*(4x,b0.8))')64_int8,64_int8
enddo
! see the BGE() description for an extended description
! of related information
end program demo_ble
Results:
-0128 F 10000000
+0064 01000000
-0096 F 10100000
+0064 01000000
-0064 F 11000000
+0064 01000000
-0032 F 11100000
+0064 01000000
+0000 T 00000000
+0064 01000000
+0032 T 00100000
+0064 01000000
+0064 T 01000000
+0064 01000000
+0096 F 01100000
+0064 01000000
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
blt#
Name#
blt(3) - [BIT:COMPARE] Bitwise less than
Synopsis#
result = blt(i,j)
elemental logical function blt(i, j)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: j
Characteristics#
i is an integer of any kind or a BOZ-literal-constant
j is an integer of any kind or a BOZ-literal-constant, not necessarily the same as i.
the result is of default logical kind
BOZ constants must have a value valid for the integer kind available with the most bits on the current platform.
Description#
blt(3) determines whether an integer is bitwise less than another.
Options#
- i
Shall be of integer type or a BOZ literal constant.
- j
Shall be of integer type or a BOZ constant.
Result#
The return value is of type logical and of the default kind.
Examples#
Sample program:
program demo_blt
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: i
integer(kind=int8) :: byte
! Compare some one-byte values to 64.
! Notice that the values are tested as bits not as integers
! so sign bits in the integer are treated just like any other
do i=-128,127,32
byte=i
write(*,'(sp,i0.4,*(1x,1l,1x,b0.8))')i,blt(byte,64_int8),byte
enddo
! BOZ literals
write(*,*)blt(z'1000', z'101011010')
! see the BGE() description for an extended description
! of related information
end program demo_blt
Results:
> -0128 F 10000000
> -0096 F 10100000
> -0064 F 11000000
> -0032 F 11100000
> +0000 T 00000000
> +0032 T 00100000
> +0064 F 01000000
> +0096 F 01100000
> T
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
bit_size#
Name#
bit_size(3) - [BIT:INQUIRY] Bit size inquiry function
Synopsis#
result = bit_size(i)
integer(kind=KIND) function bit_size(i)
integer(kind=KIND),intent(in) :: i(..)
Characteristics#
i shall be of type integer. It may be a scalar or an array.
the value of KIND is any valid value for an integer kind parameter on the processor.
the return value is a scalar of the same kind as the input value.
Description#
bit_size(3) returns the number of bits (integer precision plus sign bit) represented by the type of the integer i.
Options#
- i
An integer value of any kind whose size in bits is to be determined. Because only the type of the argument is examined, the argument need not be defined; i can be a scalar or an array, but a scalar representing just a single element is always returned.
Result#
The number of bits used to represent a value of the type and kind of i. The result is a integer scalar of the same kind as i.
Examples#
Sample program:
program demo_bit_size
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
use,intrinsic :: iso_fortran_env, only : integer_kinds
implicit none
character(len=*),parameter :: fmt=&
& '(a,": bit size is ",i3," which is kind=",i3," on this platform")'
! default integer bit size on this platform
write(*,fmt) "default", bit_size(0), kind(0)
write(*,fmt) "int8 ", bit_size(0_int8), kind(0_int8)
write(*,fmt) "int16 ", bit_size(0_int16), kind(0_int16)
write(*,fmt) "int32 ", bit_size(0_int32), kind(0_int32)
write(*,fmt) "int64 ", bit_size(0_int64), kind(0_int64)
write(*,'(a,*(i0:,", "))') "The available kinds are ",integer_kinds
end program demo_bit_size
Typical Results:
default: bit size is 32 which is kind= 4 on this platform
int8 : bit size is 8 which is kind= 1 on this platform
int16 : bit size is 16 which is kind= 2 on this platform
int32 : bit size is 32 which is kind= 4 on this platform
int64 : bit size is 64 which is kind= 8 on this platform
The available kinds are 1, 2, 4, 8, 16
Standard#
Fortran 95
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
btest#
Name#
btest(3) - [BIT:INQUIRY] Tests a bit of an integer value.
Synopsis#
result = btest(i,pos)
elemental logical function btest(i,pos)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: pos
Characteristics#
i is an integer of any kind
pos is a integer of any kind
the result is a default logical
Description#
btest(3) returns logical .true. if the bit at pos in i is set to 1. Position zero is the right-most bit. Bit position increases from right to left up to bitsize(i)-1.
Options#
- i
The integer containing the bit to be tested
- pos
The position of the bit to query. it must be a valid position for the value i; ie. 0 <= pos <= bit_size(i).
Result#
The result is a logical that has the value .true. if bit position pos of i has the value 1 and the value .false. if bit pos of i has the value 0.
Positions of bits in the sequence are numbered from right to left, with the position of the rightmost bit being zero.
Examples#
Sample program:
program demo_btest
implicit none
integer :: i, j, pos, a(2,2)
logical :: bool
character(len=*),parameter :: g='(*(g0))'
i = 32768 + 1024 + 64
write(*,'(a,i0,"=>",b32.32,/)')'Looking at the integer: ',i
! looking one bit at a time from LOW BIT TO HIGH BIT
write(*,g)'from bit 0 to bit ',bit_size(i),'==>'
do pos=0,bit_size(i)-1
bool = btest(i, pos)
write(*,'(l1)',advance='no')bool
enddo
write(*,*)
! a binary format the hard way.
! Note going from bit_size(i) to zero.
write(*,*)
write(*,g)'so for ',i,' with a bit size of ',bit_size(i)
write(*,'(b32.32)')i
write(*,g)merge('^','_',[(btest(i,j),j=bit_size(i)-1,0,-1)])
write(*,*)
write(*,g)'and for ',-i,' with a bit size of ',bit_size(i)
write(*,'(b32.32)')-i
write(*,g)merge('^','_',[(btest(-i,j),j=bit_size(i)-1,0,-1)])
! elemental:
!
a(1,:)=[ 1, 2 ]
a(2,:)=[ 3, 4 ]
write(*,*)
write(*,'(a,/,*(i2,1x,i2,/))')'given the array a ...',a
! the second bit of all the values in a
write(*,'(a,/,*(l2,1x,l2,/))')'the value of btest (a, 2)',btest(a,2)
! bits 1,2,3,4 of the value 2
write(*,'(a,/,*(l2,1x,l2,/))')'the value of btest (2, a)',btest(2,a)
end program demo_btest
Results:
> Looking at the integer: 33856=>11111111111111110111101111000000
>
> 00000000000000001000010001000000
> 11111111111111110111101111000000
> 1000010001000000
> 11111111111111110111101111000000
> from bit 0 to bit 32==>
> FFFFFFTFFFTFFFFTFFFFFFFFFFFFFFFF
>
> so for 33856 with a bit size of 32
> 00000000000000001000010001000000
> ________________^____^___^______
>
> and for -33856 with a bit size of 32
> 11111111111111110111101111000000
> ^^^^^^^^^^^^^^^^_^^^^_^^^^______
>
> given the array a ...
> 1 3
> 2 4
>
> the value of btest (a, 2)
> F F
> F T
>
> the value of btest (2, a)
> T F
> F F
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), ibclr(3), ibits(3), ibset(3), iand(3), ior(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
storage_size#
Name#
storage_size(3) - [BIT:INQUIRY] Storage size in bits
Synopsis#
result = storage_size(a [,KIND] )
integer(kind=KIND) storage_size(a,KIND)
type(TYPE(kind=**)) :: a
integer,intent(in),optional :: KIND
Characteristics#
a kind designated as ** may be any supported kind for the type
a may be of any type and kind. If it is polymorphic it shall not be an undefined pointer. If it is unlimited polymorphic or has any deferred type parameters, it shall not be an unallocated allocatable variable or a disassociated or undefined pointer.
The kind type parameter of the returned value is that specified by the value of kind; otherwise, the kind type parameter is that of default integer type.
The result is an integer scalar of default kind unless kind is specified, in which case it has the kind specified by kind.
Description#
storage_size(3) returns the storage size of argument a in bits.
Options#
- a
The entity to determine the storage size of
- kind
a scalar integer constant expression that defines the kind of the output value.
Result#
The result value is the size expressed in bits for an element of an array that has the dynamic type and type parameters of a.
If the type and type parameters are such that storage association applies, the result is consistent with the named constants defined in the intrinsic module ISO_FORTRAN_ENV.
NOTE1
An array element might take “type” more bits to store than an isolated scalar, since any hardware-imposed alignment requirements for array elements might not apply to a simple scalar variable.
NOTE2
This is intended to be the size in memory that an object takes when it is stored; this might differ from the size it takes during expression handling (which might be the native register size) or when stored in a file. If an object is never stored in memory but only in a register, this function nonetheless returns the size it would take if it were stored in memory.
Examples#
Sample program
program demo_storage_size
implicit none
! a default real, integer, and logical are the same storage size
write(*,*)'size of integer ',storage_size(0)
write(*,*)'size of real ',storage_size(0.0)
write(*,*)'size of logical ',storage_size(.true.)
write(*,*)'size of complex ',storage_size((0.0,0.0))
! note the size of an element of the array, not the storage size of
! the entire array is returned for array arguments
write(*,*)'size of integer array ',storage_size([0,1,2,3,4,5,6,7,8,9])
end program demo_storage_size
Results:
size of integer 32
size of real 32
size of logical 32
size of complex 64
size of integer array 32
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions
leadz#
Name#
leadz(3) - [BIT:COUNT] Number of leading zero bits of an integer
Synopsis#
result = leadz(i)
elemental integer function leadz(i)
integer(kind=**),intent(in) :: i
Characteristics#
i may be an integer of any kind.
the return value is a default integer type.
Description#
leadz(3) returns the number of leading zero bits of an integer.
Options#
- i
integer to count the leading zero bits of.
Result#
The number of leading zero bits, taking into account the kind of the input value. If all the bits of i are zero, the result value is bit_size(i).
The result may also be thought of as bit_size(i)-1-k where k is the position of the leftmost 1 bit in the input i. Positions are from 0 to bit-size(), with 0 at the right-most bit.
Examples#
Sample program:
program demo_leadz
implicit none
integer :: value, i
character(len=80) :: f
! make a format statement for writing a value as a bit string
write(f,'("(b",i0,".",i0,")")')bit_size(value),bit_size(value)
! show output for various integer values
value=0
do i=-150, 150, 50
value=i
write (*,'("LEADING ZERO BITS=",i3)',advance='no') leadz(value)
write (*,'(" OF VALUE ")',advance='no')
write(*,f,advance='no') value
write(*,'(*(1x,g0))') "AKA",value
enddo
! Notes:
! for two's-complements programming environments a negative non-zero
! integer value will always start with a 1 and a positive value with 0
! as the first bit is the sign bit. Such platforms are very common.
end program demo_leadz
Results:
LEADING ZERO BITS= 0 OF VALUE 11111111111111111111111101101010 AKA -150
LEADING ZERO BITS= 0 OF VALUE 11111111111111111111111110011100 AKA -100
LEADING ZERO BITS= 0 OF VALUE 11111111111111111111111111001110 AKA -50
LEADING ZERO BITS= 32 OF VALUE 00000000000000000000000000000000 AKA 0
LEADING ZERO BITS= 26 OF VALUE 00000000000000000000000000110010 AKA 50
LEADING ZERO BITS= 25 OF VALUE 00000000000000000000000001100100 AKA 100
LEADING ZERO BITS= 24 OF VALUE 00000000000000000000000010010110 AKA 150
Standard#
Fortran 2008
See Also#
bit_size(3), popcnt(3), poppar(3), trailz(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
popcnt#
Name#
popcnt(3) - [BIT:COUNT] Number of bits set
Synopsis#
result = popcnt(i)
elemental integer function popcnt(i)
integer(kind=KIND), intent(in) :: i
Characteristics#
i may be an integer of any kind.
The return value is an integer of the default integer kind.
Description#
popcnt(3) returns the number of bits set to one in the binary representation of an integer.
Options#
- i
value to count set bits in
Result#
The number of bits set to one in i.
Examples#
Sample program:
program demo_popcnt
use, intrinsic :: iso_fortran_env, only : integer_kinds, &
& int8, int16, int32, int64
implicit none
character(len=*),parameter :: pretty='(b64,1x,i0)'
! basic usage
print pretty, 127, popcnt(127)
print pretty, int(b"01010"), popcnt(int(b"01010"))
! any kind of an integer can be used
print pretty, huge(0_int8), popcnt(huge(0_int8))
print pretty, huge(0_int16), popcnt(huge(0_int16))
print pretty, huge(0_int32), popcnt(huge(0_int32))
print pretty, huge(0_int64), popcnt(huge(0_int64))
end program demo_popcnt
Results:
Note that on most machines the first bit is the sign bit, and a zero is used for positive values; but that this is system-dependent. These are typical values, where the huge(3f) function has set all but the first bit to 1.
> 1111111 7
> 1010 2
> 1111111 7
> 111111111111111 15
> 1111111111111111111111111111111 31
> 111111111111111111111111111111111111111111111111111111111111111 63
Standard#
Fortran 2008
See Also#
There are many procedures that operator or query values at the bit level:
poppar(3), leadz(3), trailz(3) atomic_and(3), atomic_fetch_and(3), atomic_fetch_or(3), atomic_fetch_xor(3), atomic_or(3), atomic_xor(3), bge(3), bgt(3), bit_size(3), ble(3), blt(3), btest(3), dshiftl(3), dshiftr(3), iall(3), iand(3), iany(3), ibclr(3), ibits(3), ibset(3), ieor(3), ior(3), iparity(3), ishftc(3), ishft(3), maskl(3), maskr(3), merge_bits(3), mvbits(3), not(3), shifta(3), shiftl(3), shiftr(3), storage_size(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
poppar#
Name#
poppar(3) - [BIT:COUNT] Parity of the number of bits set
Synopsis#
result = poppar(i)
elemental integer function poppar(i)
integer(kind=KIND), intent(in) :: i
Characteristics#
i is an integer of any kind
the return value is a default kind integer
Description#
poppar(3) returns the parity of an integer’s binary representation (i.e., the parity of the number of bits set).
The parity is expressed as
0 (zero) if i has an even number of bits set to 1.
1 (one) if the number of bits set to one 1 is odd,
Options#
- i
The value to query for its bit parity
Result#
The return value is equal to 0 if i has an even number of bits set and 1 if an odd number of bits are set.
Examples#
Sample program:
program demo_poppar
use, intrinsic :: iso_fortran_env, only : integer_kinds, &
& int8, int16, int32, int64
implicit none
character(len=*),parameter :: pretty='(b64,1x,i0)'
! basic usage
print pretty, 127, poppar(127)
print pretty, 128, poppar(128)
print pretty, int(b"01010"), poppar(int(b"01010"))
! any kind of an integer can be used
print pretty, huge(0_int8), poppar(huge(0_int8))
print pretty, huge(0_int16), poppar(huge(0_int16))
print pretty, huge(0_int32), poppar(huge(0_int32))
print pretty, huge(0_int64), poppar(huge(0_int64))
end program demo_poppar
Results:
> 1111111 1
> 10000000 1
> 1010 0
> 1111111111111111111111111111111 1
> 1111111 1
> 111111111111111 1
> 1111111111111111111111111111111 1
> 111111111111111111111111111111111111111111111111111111111111111 1
Standard#
Fortran 2008
See Also#
There are many procedures that operator or query values at the bit level:
popcnt(3), leadz(3), trailz(3) atomic_and(3), atomic_fetch_and(3), atomic_fetch_or(3), atomic_fetch_xor(3), atomic_or(3), atomic_xor(3), bge(3), bgt(3), bit_size(3), ble(3), blt(3), btest(3), dshiftl(3), dshiftr(3), iall(3), iand(3), iany(3), ibclr(3), ibits(3), ibset(3), ieor(3), ior(3), iparity(3), ishftc(3), ishft(3), maskl(3), maskr(3), merge_bits(3), mvbits(3), not(3), shifta(3), shiftl(3), shiftr(3), storage_size(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
trailz#
Name#
trailz(3) - [BIT:COUNT] Number of trailing zero bits of an integer
Synopsis#
result = trailz(i)
elemental integer function trailz(i)
integer(kind=**),intent(in) :: i
Characteristics#
i is an integer of any kind.
the result is an integer of default kind
Description#
trailz(3) returns the number of trailing zero bits of an integer value.
Options#
- i
the value to count trailing zero bits in
Result#
The number of trailing rightmost zero bits in an integer value after the last non-zero bit.
> right-most non-zero bit
> V
> |0|0|0|1|1|1|0|1|0|0|0|0|0|0|
> ^ |___________| trailing zero bits
> bit_size(i)
If all the bits of i are zero, the result is the size of the input value in bits, ie. bit_size(i).
The result may also be seen as the position of the rightmost 1 bit in i, starting with the rightmost bit being zero and counting to the left.
Examples#
Sample program:
program demo_trailz
! some common integer kinds
use, intrinsic :: iso_fortran_env, only : &
& integer_kinds, int8, int16, int32, int64
implicit none
! a handy format
character(len=*),parameter :: &
& show = '(1x,"value=",i4,", value(bits)=",b32.32,1x,", trailz=",i3)'
integer(kind=int64) :: bigi
! basics
write(*,*)'Note default integer is',bit_size(0),'bits'
print show, -1, -1, trailz(-1)
print show, 0, 0, trailz(0)
print show, 1, 1, trailz(1)
print show, 96, 96, trailz(96)
! elemental
print *, 'elemental and any integer kind:'
bigi=2**5
write(*,*) trailz( [ bigi, bigi*256, bigi/2 ] )
write(*,'(1x,b64.64)')[ bigi, bigi*256, bigi/2 ]
end program demo_trailz
Results:
Note default integer is 32 bits
value= -1, value(bits)=11111111111111111111111111111111 , trailz= 0
value= 0, value(bits)=00000000000000000000000000000000 , trailz= 32
value= 1, value(bits)=00000000000000000000000000000001 , trailz= 0
value= 96, value(bits)=00000000000000000000000001100000 , trailz= 5
elemental and any integer kind:
5 13 4
0000000000000000000000000000000000000000000000000000000000100000
0000000000000000000000000000000000000000000000000010000000000000
0000000000000000000000000000000000000000000000000000000000010000
Standard#
Fortran 2008
See Also#
bit_size(3), popcnt(3), poppar(3), leadz(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
dshiftl#
Name#
dshiftl(3) - [BIT:COPY] Combined left shift of the bits of two integers
Synopsis#
result = dshiftl(i, j, shift)
elemental integer(kind=KIND) function dshiftl(i, j, shift)
integer(kind=KIND),intent(in) :: i
integer(kind=KIND),intent(in) :: j
integer(kind=**),intent(in) :: shift
Characteristics#
the kind of i, j, and the return value are the same. An exception is that one of i and j may be a BOZ literal constant (A BOZ literal constant is a binary, octal or hex constant).
If either I or J is a BOZ-literal-constant (but not both), it is first converted as if by the intrinsic function int(3) to type integer with the kind type parameter of the other.
a kind designated as ** may be any supported kind for the type
Description#
dshiftl(3) combines bits of i and j. The rightmost shift bits of the result are the leftmost shift bits of j, and the remaining bits are the rightmost bitsize(i)-shift of i.
Hence dshiftl is designated as a “combined left shift”, because it is like we appended i and j together, shifted it shift bits to the left, and then kept the same number of bits as i or j had.
For example, for two 16-bit values if shift=6
SHIFT=6
I = 1111111111111111
J = 0000000000000000
COMBINED 11111111111111110000000000000000
DROP LEFT BITS 11111111110000000000000000
KEEP LEFT 16 1111111111000000
NOTE#
This is equivalent to
ior( shiftl(i, shift), shiftr(j, bit_size(j) - shift) )
Also note that using this last representation of the operation is can be derived that when both i and j have the same value as in
dshiftl(i, i, shift)
the result has the same value as a circular shift:
ishftc(i, shift)
Options#
- i
used to define the left pattern of bits in the combined pattern
- j
used for the right pattern of bits in the combined pattern
- shift
shall be nonnegative and less than or equal to the number of bits in an integer input value (ie. the bit size of either one that is not a BOZ literal constant).
Result#
The leftmost shift bits of j are copied to the rightmost bits of the result, and the remaining bits are the rightmost bits of i.
Examples#
Sample program:
program demo_dshiftl
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int32) :: i, j
integer :: shift
! basic usage
write(*,*) dshiftl (1, 2**30, 2) ! int32 values on little-endian => 5
! print some simple calls as binary to better visual the results
i=-1
j=0
shift=5
call printit()
! the leftmost SHIFT bits of J are copied to the rightmost result bits
j=int(b"11111000000000000000000000000000")
! and the other bits are the rightmost bits of I
i=int(b"00000000000000000000000000000000")
call printit()
j=int(b"11111000000000000000000000000000")
i=int(b"00000111111111111111111111111111")
! result should be all 1s
call printit()
contains
subroutine printit()
! print i,j,shift and then i,j, and the result as binary values
write(*,'(*(g0))')'I=',i,' J=',j,' SHIFT=',shift
write(*,'(b32.32)') i,j, dshiftl (i, j, shift)
end subroutine printit
end program demo_dshiftl
Results:
> I=-1 J=0 SHIFT=5
> 11111111111111111111111111111111
> 00000000000000000000000000000000
> 11111111111111111111111111100000
> I=0 J=-134217728 SHIFT=5
> 00000000000000000000000000000000
> 11111000000000000000000000000000
> 00000000000000000000000000011111
> I=134217727 J=-134217728 SHIFT=5
> 00000111111111111111111111111111
> 11111000000000000000000000000000
> 11111111111111111111111111111111
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
dshiftr#
Name#
dshiftr(3) - [BIT:COPY] Combined right shift of the bits of two integers
Synopsis#
result = dshiftr(i, j, shift)
elemental integer(kind=KIND) function dshiftr(i, j, shift)
integer(kind=KIND),intent(in) :: i
integer(kind=KIND),intent(in) :: j
integer(kind=**),intent(in) :: shift
Characteristics#
a kind designated as ** may be any kind value for the integer type
the kind of i, j, and the return value are the same. An exception is that one of i and j may be a BOZ literal constant (A BOZ literal constant is a binary, octal or hex constant).
If either I or J is a BOZ-literal-constant, it is first converted as if by the intrinsic function int(3) to type integer with the kind type parameter of the other.
Description#
dshiftr(3) combines bits of i and j. The leftmost shift bits of the result are the rightmost shift bits of i, and the remaining bits are the leftmost bits of j.
It may be thought of as appending the bits of i and j, dropping off the shift rightmost bits, and then retaining the same number of rightmost bits as an input value, hence the name “combined right shift”…
Given two 16-bit values labeled alphabetically …
i=ABCDEFGHIJKLMNOP
j=abcdefghijklmnop
Append them together
ABCDEFGHIJKLMNOPabcdefghijklmnop
Shift them N=6 bits to the right dropping off bits
ABCDEFGHIJKLMNOPabcdefghij
Keep the 16 right-most bits
KLMNOPabcdefghij
NOTE#
dshifr(i,j,shift) is equivalent to
ior(shiftl (i, bit_size(i) - shift), shiftr(j, shift) )
it can also be seen that if i and j have the same value
dshiftr( i, i, shift )
this has the same result as a negative circular shift
ishftc( i, -shift ).
Options#
- i
left value of the pair of values to be combine-shifted right
- j
right value of the pair of values to be combine-shifted right
- shift
the shift value is non-negative and less than or equal to the number of bits in an input value as can be computed by bit_size(3).
Result#
The result is a combined right shift of i and j that is the same as the bit patterns of the inputs being combined left to right, dropping off shift bits on the right and then retaining the same number of bits as an input value from the rightmost bits.
Examples#
Sample program:
program demo_dshiftr
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int32) :: i, j
integer :: shift
! basic usage
write(*,*) dshiftr (1, 2**30, 2)
! print some calls as binary to better visualize the results
i=-1
j=0
shift=5
! print values
write(*,'(*(g0))')'I=',i,' J=',j,' SHIFT=',shift
write(*,'(b32.32)') i,j, dshiftr (i, j, shift)
! visualizing a "combined right shift" ...
i=int(b"00000000000000000000000000011111")
j=int(b"11111111111111111111111111100000")
! appended together ( i//j )
! 0000000000000000000000000001111111111111111111111111111111100000
! shifted right SHIFT values dropping off shifted values
! 00000000000000000000000000011111111111111111111111111111111
! keep enough rightmost bits to fill the kind
! 11111111111111111111111111111111
! so the result should be all 1s bits ...
write(*,'(*(g0))')'I=',i,' J=',j,' SHIFT=',shift
write(*,'(b32.32)') i,j, dshiftr (i, j, shift)
end program demo_dshiftr
Results:
> 1342177280
> I=-1 J=0 SHIFT=5
> 11111111111111111111111111111111
> 00000000000000000000000000000000
> 11111000000000000000000000000000
> I=31 J=-32 SHIFT=5
> 00000000000000000000000000011111
> 11111111111111111111111111100000
> 11111111111111111111111111111111
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
merge_bits#
Name#
merge_bits(3) - [BIT:COPY] Merge bits using a mask
Synopsis#
result = merge_bits(i, j, mask)
elemental integer(kind=KIND) function merge_bits(i,j,mask)
integer(kind=KIND), intent(in) :: i, j, mask
Characteristics#
the result and all input values have the same integer type and KIND with the exception that the mask and either i or j may be a BOZ constant.
Description#
A common graphics operation in Ternary Raster Operations is to combine bits from two different sources, generally referred to as bit-blending. merge_bits(3) performs a masked bit-blend of i and j using the bits of the mask value to determine which of the input values to copy bits from.
Specifically, The k-th bit of the result is equal to the k-th bit of i if the k-th bit of mask is 1; it is equal to the k-th bit of j otherwise (so all three input values must have the same number of bits).
The resulting value is the same as would result from
ior (iand (i, mask),iand (j, not (mask)))
An exception to all values being of the same integer type is that i or j and/or the mask may be a BOZ constant (A BOZ constant means it is either a Binary, Octal, or Hexadecimal literal constant). The BOZ values are converted to the integer type of the non-BOZ value(s) as if called by the intrinsic function int() with the kind of the non-BOZ value(s), so the BOZ values must be in the range of the type of the result.
Options#
- i
value to select bits from when the associated bit in the mask is 1.
- j
value to select bits from when the associated bit in the mask is 0.
- mask
a value whose bits are used as a mask to select bits from i and j
Result#
The bits blended from i and j using the mask mask.
Examples#
Sample program:
program demo_merge_bits
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int16) :: if_one,if_zero,msk
character(len=*),parameter :: fmt='(*(g0, 1X))'
! basic usage
print *,'MERGE_BITS( 5,10,41) should be 3.=>',merge_bits(5,10,41)
print *,'MERGE_BITS(13,18,22) should be 4.=>',merge_bits(13,18,22)
! use some values in base2 illustratively:
if_one =int(b'1010101010101010',kind=int16)
if_zero=int(b'0101010101010101',kind=int16)
msk=int(b'0101010101010101',kind=int16)
print '("should get all zero bits =>",b16.16)', &
& merge_bits(if_one,if_zero,msk)
msk=int(b'1010101010101010',kind=int16)
print '("should get all ones bits =>",b16.16)', &
& merge_bits(if_one,if_zero,msk)
! using BOZ values
print fmt, &
& merge_bits(32767_int16, o'12345', 32767_int16), &
& merge_bits(o'12345', 32767_int16, b'0000000000010101'), &
& merge_bits(32767_int16, o'12345', z'1234')
! a do-it-yourself equivalent for comparison and validation
print fmt, &
& ior(iand(32767_int16, 32767_int16), &
& iand(o'12345', not(32767_int16))), &
& ior(iand(o'12345', int(o'12345', kind=int16)), &
& iand(32767_int16, not(int(o'12345', kind=int16)))), &
& ior(iand(32767_int16, z'1234'), &
& iand(o'12345', not(int( z'1234', kind=int16))))
end program demo_merge_bits
Results:
MERGE_BITS( 5,10,41) should be 3.=> 3
MERGE_BITS(13,18,22) should be 4.=> 4
should get all zero bits =>0000000000000000
should get all ones bits =>1111111111111111
32767 32751 5877
32767 32767 5877
Standard#
Fortran 2008
See also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
mvbits#
Name#
mvbits(3) - [BIT:COPY] Reproduce bit patterns found in one integer in another
Synopsis#
call mvbits(from, frompos, len, to, topos)
elemental subroutine mvbits( from, frompos, len, to, topos )
integer(kind=KIND),intent(in) :: from
integer(kind=**),intent(in) :: frompos
integer(kind=**),intent(in) :: len
integer(kind=KIND),intent(inout) :: to
integer(kind=**),intent(in) :: topos
Characteristics#
from is an integer
frompos is an integer
len is an integer
to is an integer of the same kind as from.
topos is an integer
Description#
mvbits(3) copies a bit pattern found in a range of adjacent bits in the integer from to a specified position in another integer to (which is of the same kind as from). It otherwise leaves the bits in to as-is.
The bit positions copied must exist within the value of from. That is, the values of frompos+len-1 and topos+len-1 must be nonnegative and less than bit_size(from).
The bits are numbered 0 to bit_size(i)-1, from right to left.
Options#
- from
An integer to read bits from.
- frompos
frompos is the position of the first bit to copy. It is a nonnegative integer value < bit_size(from).
- len
A nonnegative integer value that indicates how many bits to copy from from. It must not specify copying bits past the end of from. That is, frompos + len must be less than or equal to bit_size(from).
- to
The integer variable to place the copied bits into. It must be of the same kind as from and may even be the same variable as from, or associated to it.
to is set by copying the sequence of bits of length len, starting at position frompos of from to position topos of to. No other bits of to are altered. On return, the len bits of to starting at topos are equal to the value that the len bits of from starting at frompos had on entry.
- topos
A nonnegative integer value indicating the starting location in to to place the specified copy of bits from from. topos + len must be less than or equal to bit_size(to).
Examples#
Sample program that populates a new 32-bit integer with its bytes in reverse order from the input value (ie. changes the Endian of the integer).
program demo_mvbits
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int32) :: intfrom, intto, abcd_int
character(len=*),parameter :: bits= '(g0,t30,b32.32)'
character(len=*),parameter :: fmt= '(g0,t30,a,t40,b32.32)'
intfrom=huge(0) ! all bits are 1 accept the sign bit
intto=0 ! all bits are 0
!! CHANGE BIT 0
! show the value and bit pattern
write(*,bits)intfrom,intfrom
write(*,bits)intto,intto
! copy bit 0 from intfrom to intto to show the rightmost bit changes
! (from, frompos, len, to, topos)
call mvbits(intfrom, 0, 1, intto, 0) ! change bit 0
write(*,bits)intto,intto
!! COPY PART OF A VALUE TO ITSELF
! can copy bit from a value to itself
call mvbits(intfrom,0,1,intfrom,31)
write(*,bits)intfrom,intfrom
!! MOVING BYTES AT A TIME
! make native integer value with bit patterns
! that happen to be the same as the beginning of the alphabet
! to make it easy to see the bytes are reversed
abcd_int=transfer('abcd',0)
! show the value and bit pattern
write(*,*)'native'
write(*,fmt)abcd_int,abcd_int,abcd_int
! change endian of the value
abcd_int=int_swap32(abcd_int)
! show the values and their bit pattern
write(*,*)'non-native'
write(*,fmt)abcd_int,abcd_int,abcd_int
contains
pure elemental function int_swap32(intin) result(intout)
! Convert a 32 bit integer from big Endian to little Endian,
! or conversely from little Endian to big Endian.
!
integer(kind=int32), intent(in) :: intin
integer(kind=int32) :: intout
! copy bytes from input value to new position in output value
! (from, frompos, len, to, topos)
call mvbits(intin, 0, 8, intout, 24) ! byte1 to byte4
call mvbits(intin, 8, 8, intout, 16) ! byte2 to byte3
call mvbits(intin, 16, 8, intout, 8) ! byte3 to byte2
call mvbits(intin, 24, 8, intout, 0) ! byte4 to byte1
end function int_swap32
end program demo_mvbits
Results:
2147483647 01111111111111111111111111111111
0 00000000000000000000000000000000
1 00000000000000000000000000000001
-1 11111111111111111111111111111111
native
1684234849 abcd 01100100011000110110001001100001
non-native
1633837924 dcba 01100001011000100110001101100100
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), btest(3), ibclr(3), ibits(3), ibset(3), iand(3), ior(3), ieor(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ibits#
Name#
ibits(3) - [BIT:COPY] Extraction of a subset of bits
Synopsis#
result = ibits(i, pos, len)
elemental integer(kind=KIND) function ibits(i,pos,len)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: pos
integer(kind=**),intent(in) :: len
Characteristics#
a kind designated as ** may be any supported integer kind
i may be any supported integer kind as well
the return value will be the same kind as i
Description#
ibits(3) extracts a field of bits from i, starting from bit position pos and extending left for a total of len bits.
The result is then right-justified and the remaining left-most bits in the result are zeroed.
The position pos is calculated assuming the right-most bit is zero and the positions increment to the left.
Options#
- i
The value to extract bits from
- pos
The position of the bit to start copying at. pos is non-negative.
- len
the number of bits to copy from i. It must be non-negative.
pos + len shall be less than or equal to bit_size(i).
Result#
The return value is composed of the selected bits right-justified, left-padded with zeros.
Examples#
Sample program:
program demo_ibits
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int16) :: i,j
! basic usage
print *,ibits (14, 1, 3) ! should be seven
print *,ibits(-1,10,3) ! and so is this
! it is easier to see using binary representation
i=int(b'0101010101011101',kind=int16)
write(*,'(b16.16,1x,i0)') ibits(i,3,3), ibits(i,3,3)
! we can illustrate this as
! #-- position 15
! | #-- position 0
! | <-- +len |
! V V
! 5432109876543210
i =int(b'1111111111111111',kind=int16)
! ^^^^
j=ibits(i,10,4) ! start at 10th from left and proceed
! left for a total of 4 characters
write(*,'(a,b16.16)')'j=',j
! lets do something less ambiguous
i =int(b'0010011000000000',kind=int16)
j=ibits(i,9,5)
write(*,'(a,b16.16)')'j=',j
end program demo_ibits
Results:
> 7
> 7
> 0000000000000011 3
> j=0000000000001111
> j=0000000000010011
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), btest(3), ibclr(3), ibset(3), iand(3), ior(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ibclr#
Name#
ibclr(3) - [BIT:SET] Clear a bit
Synopsis#
result = ibclr(i, pos)
elemental integer(kind=KIND) function ibclr(i,pos)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: pos
Characteristics#
i shall be type integer.
pos shall be type integer.
The return value is of the same kind as i.
a kind designated as ** may be any supported kind for the type
Description#
ibclr(3) returns the value of i with the bit at position pos set to zero.
Options#
- i
The initial value to be modified
- pos
The position of the bit to change in the input value. A value of zero refers to the right-most bit. The value of pos must be nonnegative and less than (bit_size(i)).
Result#
The returned value has the same bit sequence as i except the designated bit is unconditionally set to 0
Examples#
Sample program:
program demo_ibclr
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int16) :: i
! basic usage
print *,ibclr (16, 1), ' ==> ibclr(16,1) has the value 15'
! it is easier to see using binary representation
i=int(b'0000000000111111',kind=int16)
write(*,'(b16.16,1x,i0)') ibclr(i,3), ibclr(i,3)
! elemental
print *,'an array of initial values may be given as well'
print *,ibclr(i=[7,4096,9], pos=2)
print *
print *,'a list of positions results in multiple returned values'
print *,'not multiple bits set in one value, as the routine is '
print *,'a scalar function; calling it elementally essentially '
print *,'calls it multiple times. '
write(*,'(b16.16)') ibclr(i=-1_int16, pos=[1,2,3,4])
! both may be arrays if of the same size
end program demo_ibclr
Results:
> 16 ==> ibclr(16,1) has the value 15
> 0000000000110111 55
> an array of initial values may be given as well
> 3 4096 9
>
> a list of positions results in multiple returned values
> not multiple bits set in one value, as the routine is
> a scalar function; calling it elementally essentially
> calls it multiple times.
> 1111111111111101
> 1111111111111011
> 1111111111110111
> 1111111111101111
Standard#
Fortran 95
See Also#
ieor(3), not(3), btest(3), ibset(3), ibits(3), iand(3), ior(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ibset#
Name#
ibset(3) - [BIT:SET] Set a bit to one in an integer value
Synopsis#
result = ibset(i, pos)
elemental integer(kind=KIND) function ibset(i,pos)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: pos
Characteristics#
a kind designated as ** may be any supported kind for the type
The return value is of the same kind as i. Otherwise, any integer kinds are allowed.
Description#
ibset(3) returns the value of i with the bit at position pos set to one.
Options#
- i
The initial value to be modified
- pos
The position of the bit to change in the input value. A value of zero refers to the right-most bit. The value of pos must be nonnegative and less than (bit_size(i)).
Result#
The returned value has the same bit sequence as i except the designated bit is unconditionally set to 1.
Examples#
Sample program:
program demo_ibset
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int16) :: i
! basic usage
print *,ibset (12, 1), 'ibset(12,1) has the value 14'
! it is easier to see using binary representation
i=int(b'0000000000000110',kind=int16)
write(*,'(b16.16,1x,i0,1x,i0)') ibset(i,12), ibset(i,12), i
! elemental
print *,'an array of initial values may be given as well'
print *,ibset(i=[0,4096], pos=2)
print *
print *,'a list of positions results in multiple returned values'
print *,'not multiple bits set in one value, as the routine is '
print *,'a scalar function; calling it elementally essentially '
print *,'calls it multiple times. '
write(*,'(b16.16)') ibset(i=0, pos=[1,2,3,4])
! both may be arrays if of the same size
end program demo_ibset
Results:
> 14 ibset(12,1) has the value 14
> 0001000000000110 4102 6
> an array of initial values may be given as well
> 4 4100
>
> a list of positions results in multiple returned values
> not multiple bits set in one value, as the routine is
> a scalar function; calling it elementally essentially
> calls it multiple times.
> 0000000000000010
> 0000000000000100
> 0000000000001000
> 0000000000010000
Standard#
Fortran 95
See Also#
ieor(3), not(3), btest(3), ibits(3), iand(3), ior(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
maskl#
Name#
maskl(3) - [BIT:SET] Generates a left justified mask
Synopsis#
result = maskl( i [,kind] )
elemental integer(kind=KIND) function maskl(i,KIND)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in),optional :: KIND
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer
kind Shall be a scalar constant expression of type integer whose value is a supported integer kind.
The result is an integer of the same kind as i unless kind is present, which is then used to specify the kind of the result.
Description#
maskl(3) has its leftmost i bits set to 1, and the remaining bits set to 0.
Options#
- i
the number of left-most bits to set in the integer result. It must be from 0 to the number of bits for the kind of the result. The default kind of the result is the same as i unless the result size is specified by kind. That is, these Fortran statements must be .true. :
i >= 0 .and. i < bitsize(i) ! if KIND is not specified
i >= 0 .and. i < bitsize(0_KIND) ! if KIND is specified
- kind
designates the kind of the integer result.
Result#
The leftmost i bits of the output integer are set to 1 and the other bits are set to 0.
Examples#
Sample program:
program demo_maskl
implicit none
integer :: i
! basics
i=3
write(*,'(i0,1x,b0)') i, maskl(i)
! elemental
write(*,'(*(i11,1x,b0.32,1x,/))') maskl([(i,i,i=0,bit_size(0),4)])
end program demo_maskl
Results:
> 3 11100000000000000000000000000000
> 0 00000000000000000000000000000000
> -268435456 11110000000000000000000000000000
> -16777216 11111111000000000000000000000000
> -1048576 11111111111100000000000000000000
> -65536 11111111111111110000000000000000
> -4096 11111111111111111111000000000000
> -256 11111111111111111111111100000000
> -16 11111111111111111111111111110000
> -1 11111111111111111111111111111111
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
maskr#
Name#
maskr(3) - [BIT:SET] Generates a right-justified mask
Synopsis#
result = maskr( i [,kind] )
elemental integer(kind=KIND) function maskr(i,KIND)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in),optional :: KIND
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer
kind Shall be a scalar constant expression of type integer whose value is a supported integer kind.
The result is an integer of the same kind as i unless kind is present, which is then used to specify the kind of the result.
Description#
maskr(3) generates an integer with its rightmost i bits set to 1, and the remaining bits set to 0.
Options#
- i
the number of right-most bits to set in the integer result. It must be from 0 to the number of bits for the kind of the result. The default kind of the result is the same as i unless the result size is specified by kind. That is, these Fortran statements must be .true. :
i >= 0 .and. i < bitsize(i) ! if KIND is not specified
i >= 0 .and. i < bitsize(0_KIND) ! if KIND is specified
- kind
designates the kind of the integer result.
Result#
The rightmost i bits of the output integer are set to 1 and the other bits are set to 0.
Examples#
Sample program:
program demo_maskr
implicit none
integer :: i
! basics
print *,'basics'
write(*,'(i0,t5,b32.32)') 1, maskr(1)
write(*,'(i0,t5,b32.32)') 5, maskr(5)
write(*,'(i0,t5,b32.32)') 11, maskr(11)
print *,"should be equivalent on two's-complement processors"
write(*,'(i0,t5,b32.32)') 1, shiftr(-1,bit_size(0)-1)
write(*,'(i0,t5,b32.32)') 5, shiftr(-1,bit_size(0)-5)
write(*,'(i0,t5,b32.32)') 11, shiftr(-1,bit_size(0)-11)
! elemental
print *,'elemental '
print *,'(array argument accepted like called with each element)'
write(*,'(*(i11,1x,b0.32,1x,/))') maskr([(i,i,i=0,bit_size(0),4)])
end program demo_maskr
Results:
> basics
> 1 00000000000000000000000000000001
> 5 00000000000000000000000000011111
> 11 00000000000000000000011111111111
> should be equivalent on two's-complement processors
> 1 00000000000000000000000000000001
> 5 00000000000000000000000000011111
> 11 00000000000000000000011111111111
> elemental
> (array argument accepted like called with each element)
> 0 00000000000000000000000000000000
> 15 00000000000000000000000000001111
> 255 00000000000000000000000011111111
> 4095 00000000000000000000111111111111
> 65535 00000000000000001111111111111111
> 1048575 00000000000011111111111111111111
> 16777215 00000000111111111111111111111111
> 268435455 00001111111111111111111111111111
> -1 11111111111111111111111111111111
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
iparity#
Name#
iparity(3) - [BIT:LOGICAL] Bitwise exclusive OR of array elements
Synopsis#
result = iparity( array [,mask] ) | iparity( array, dim [,mask] )
integer(kind=KIND) function iparity(array, dim, mask )
integer(kind=KIND),intent(in) :: array(..)
logical(kind=**),intent(in),optional :: dim
logical(kind=**),intent(in),optional :: mask(..)
array - An integer array.
dim - an integer scalar from 1 to the rank of array
mask - logical conformable with array.
Description#
iparity(3) reduces with bitwise xor (exclusive or) the elements of array along dimension dim if the corresponding element in mask is .true..
Options#
- array
an array of integer values
dim a value from 1 to the rank of array.
- mask
a logical mask either a scalar or an array of the same shape as array.
Result#
The result is of the same type as array.
If dim is absent, a scalar with the bitwise xor of all elements in array is returned. Otherwise, an array of rank n-1, where n equals the rank of array, and a shape similar to that of array with dimension dim dropped is returned.
Case (i): The result of IPARITY (ARRAY) has a value equal to the bitwise exclusive OR of all the elements of ARRAY. If ARRAY has size zero the result has the value zero.
Case (ii): The result of IPARITY (ARRAY, MASK=MASK) has a value equal to that of
IPARITY (PACK (ARRAY, MASK)).
Case (iii): The result of IPARITY (ARRAY, DIM=DIM [, MASK=MASK]) has a value equal to that of IPARITY (ARRAY [, MASK=MASK]) if ARRAY has rank one.
Otherwise, an array of values reduced along the dimension
**dim** is returned.
Examples#
Sample program:
program demo_iparity
implicit none
integer, dimension(2) :: a
a(1) = int(b'00100100')
a(2) = int(b'01101010')
print '(b8.8)', iparity(a)
end program demo_iparity
Results:
01001110
Standard#
Fortran 2008
See Also#
iany(3), iall(3), ieor(3), parity(3)
fortran-lang intrinsic descriptions
iall#
Name#
iall(3) - [BIT:LOGICAL] Bitwise and of array elements
Synopsis#
result = iall(array [,mask]) | iall(array ,dim [,mask])
integer(kind=KIND) function iall(array,dim,mask)
integer(kind=KIND),intent(in) :: array(*)
integer(kind=**),intent(in),optional :: dim
logical(kind=**),intent(in),optional :: mask(*)
Characteristics#
a kind designated as ** may be any supported kind for the type
array must be an integer array
mask is a logical array that conforms to array of any logical kind.
dim may be of any integer kind.
The result will by of the same type and kind as array.
Description#
iall(3) reduces with a bitwise and the elements of array along dimension dim if the corresponding element in mask is .true..
Options#
- array
Shall be an array of type integer
- dim
(Optional) shall be a scalar of type integer with a value in the range from 1 to n, where n equals the rank of array.
- mask
(Optional) shall be of type logical and either be a scalar or an array of the same shape as array.
Result#
The result is of the same type as array.
If dim is absent, a scalar with the bitwise all of all elements in array is returned. Otherwise, an array of rank n-1, where n equals the rank of array, and a shape similar to that of array with dimension dim dropped is returned.
Examples#
Sample program:
program demo_iall
use, intrinsic :: iso_fortran_env, only : integer_kinds, &
& int8, int16, int32, int64
implicit none
integer(kind=int8) :: a(2)
a(1) = int(b'00100100')
a(2) = int(b'01101010')
print '(b8.8)', iall(a)
end program demo_iall
Results:
> 00100000
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
iand#
Name#
iand(3) - [BIT:LOGICAL] Bitwise logical AND
Synopsis#
result = iand(i, j)
elemental integer(kind=KIND) function iand(i,j)
integer(kind=KIND),intent(in) :: i
integer(kind=KIND),intent(in) :: j
Characteristics#
i, j and the result shall have the same integer type and kind, with the exception that one of i or j may be a BOZ constant.
Description#
iand(3) returns the bitwise logical and of two values.
Options#
- i
one of the pair of values to compare the bits of
- j
one of the pair of values to compare the bits of
If either i or j is a BOZ-literal-constant, it is first converted as if by the intrinsic function int(3) to type integer with the kind type parameter of the other.
Result#
The result has the value obtained by combining i and i bit-by-bit according to the following table:
I | J | IAND (I, J)
----------------------------
1 | 1 | 1
1 | 0 | 0
0 | 1 | 0
0 | 0 | 0
So if both the bit in i and j are on the resulting bit is on (a one); else the resulting bit is off (a zero).
This is commonly called the “bitwise logical AND” of the two values.
Examples#
Sample program:
program demo_iand
implicit none
integer :: a, b
data a / z'f' /, b / z'3' /
write (*,*) 'a=',a,' b=',b,'iand(a,b)=',iand(a, b)
write (*,'(b32.32)') a,b,iand(a,b)
end program demo_iand
Results:
a= 15 b= 3 iand(a,b)= 3
00000000000000000000000000001111
00000000000000000000000000000011
00000000000000000000000000000011
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), btest(3), ibclr(3), ibits(3), ibset(3), ior(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
iany#
Name#
iany(3) - [BIT:LOGICAL] Bitwise OR of array elements
Synopsis#
result = iany(array [,mask]) | iany(array ,dim [,mask])
integer(kind=KIND) function iany(array,dim,mask)
integer(kind=KIND),intent(in) :: array(..)
integer(kind=**),intent(in),optional :: dim
logical(kind=**),intent(in),optional :: mask(..)
Characteristics#
array is an integer array
dim may be of any integer kind.
mask is a logical array that conforms to array
The result will by of the same type and kind as array. It is scalar if dim does not appear or is 1. Otherwise, it is the shape and rank of array reduced by the dimension dim.
note a kind designated as ** may be any supported kind for the type
Description#
iany(3) reduces with bitwise OR (inclusive OR) the elements of array along dimension dim if the corresponding element in mask is .true..
Options#
- array
an array of elements to selectively OR based on the mask.
- dim
a value in the range from 1 to n, where n equals the rank of array.
- mask
a logical scalar; or an array of the same shape as array.
Result#
The result is of the same type as array.
If dim is absent, a scalar with the bitwise or of all elements in array is returned. Otherwise, an array of rank n-1, where n equals the rank of array, and a shape similar to that of array with dimension dim dropped is returned.
Examples#
Sample program:
program demo_iany
use, intrinsic :: iso_fortran_env, only : integer_kinds, &
& int8, int16, int32, int64
implicit none
logical,parameter :: T=.true., F=.false.
integer(kind=int8) :: a(3)
a(1) = int(b'00100100',int8)
a(2) = int(b'01101010',int8)
a(3) = int(b'10101010',int8)
write(*,*)'A='
print '(1x,b8.8)', a
print *
write(*,*)'IANY(A)='
print '(1x,b8.8)', iany(a)
print *
write(*,*)'IANY(A) with a mask'
print '(1x,b8.8)', iany(a,mask=[T,F,T])
print *
write(*,*)'should match '
print '(1x,b8.8)', iany([a(1),a(3)])
print *
write(*,*)'does it?'
write(*,*)iany(a,[T,F,T]) == iany([a(1),a(3)])
end program demo_iany
Results:
A=
00100100
01101010
10101010
IANY(A)=
11101110
IANY(A) with a mask
10101110
should match
10101110
does it?
T
Standard#
Fortran 2008
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ieor#
Name#
ieor(3) - [BIT:LOGICAL] Bitwise exclusive OR
Synopsis#
result = ieor(i, j)
elemental integer(kind=**) function ieor(i,j)
integer(kind=**),intent(in) :: i
integer(kind=**),intent(in) :: j
Characteristics#
i, j and the result must be of the same integer kind.
An exception is that one of i and j may be a BOZ literal constant
Description#
ieor(3) returns a bitwise exclusive-or of i and j.
An exclusive OR or “exclusive disjunction” is a logical operation that is true if and only if its arguments differ. In this case a one-bit and a zero-bit substitute for true and false.
This is often represented with the notation “XOR”, for “eXclusive OR”.
An alternate way to view the process is that the result has the value obtained by combining i and j bit-by-bit according to the following table:
> I | J |IEOR (I, J)
> --#---#-----------
> 1 | 1 | 0
> 1 | 0 | 1
> 0 | 1 | 1
> 0 | 0 | 0
Options#
- i
the first of the two values to XOR
- j
the second of the two values to XOR
If either I or J is a boz-literal-constant, it is first converted as if by the intrinsic function INT to type integer with the kind type parameter of the other.
Result#
If a bit is different at the same location in i and j the corresponding bit in the result is 1, otherwise it is 0.
Examples#
Sample program:
program demo_ieor
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int16) :: i,j
! basic usage
print *,ieor (16, 1), ' ==> ieor(16,1) has the value 17'
! it is easier to see using binary representation
i=int(b'0000000000111111',kind=int16)
j=int(b'0000001111110000',kind=int16)
write(*,'(a,b16.16,1x,i0)')'i= ',i, i
write(*,'(a,b16.16,1x,i0)')'j= ',j, j
write(*,'(a,b16.16,1x,i0)')'result=',ieor(i,j), ieor(i,j)
! elemental
print *,'arguments may be arrays. If both are arrays they '
print *,'must have the same shape. '
print *,ieor(i=[7,4096,9], j=2)
! both may be arrays if of the same size
end program demo_ieor
Results:
> 17 ==> ieor(16,1) has the value 17
> i= 0000000000111111 63
> j= 0000001111110000 1008
> result=0000001111001111 975
> arguments may be arrays. If both are arrays they
> must have the same shape.
> 5 4098 11
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), btest(3), ibclr(3), ibits(3), ibset(3), iand(3), ior(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ior#
Name#
ior(3) - [BIT:LOGICAL] Bitwise logical inclusive OR
Synopsis#
result = ior(i, j)
elemental integer(kind=KIND) function ior(i,j)
integer(kind=KIND ,intent(in) :: i
integer(kind=KIND ,intent(in) :: j
Characteristics#
i, j and the result shall have the same integer type and kind, with the exception that one of i or j may be a BOZ constant.
Description#
ior(3) returns the bit-wise Boolean inclusive-or of i and j.
Options#
- i
one of the pair of values to compare the bits of
- j
one of the pair of values to compare the bits of
If either i or j is a BOZ-literal-constant, it is first converted as if by the intrinsic function int(3) to type integer with the kind type parameter of the other.
Result#
The result has the value obtained by combining I and J bit-by-bit according to the following table:
I J IOR (I, J)
1 1 1
1 0 1
0 1 1
0 0 0
Where if the bit is set in either input value, it is set in the result. Otherwise the result bit is zero.
This is commonly called the “bitwise logical inclusive OR” of the two values.
Examples#
Sample program:
program demo_ior
implicit none
integer :: i, j, k
i=53 ! i=00110101 binary (lowest order byte)
j=45 ! j=00101101 binary (lowest order byte)
k=ior(i,j) ! k=00111101 binary (lowest order byte), k=61 decimal
write(*,'(i8,1x,b8.8)')i,i,j,j,k,k
end program demo_ior
Results:
53 00110101
45 00101101
61 00111101
Standard#
Fortran 95
See Also#
ieor(3), ibclr(3), not(3), btest(3), ibclr(3), ibits(3), ibset(3), iand(3), ieor(3), mvbits(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
not#
Name#
not(3) - [BIT:LOGICAL] Logical negation; flips all bits in an integer
Synopsis#
result = not(i)
elemental integer(kind=KIND) function not(i)
integer(kind=KIND), intent(in) :: i
Characteristics#
i may be an integer of any valid kind
The returned integer is of the same kind as the argument i.
Description#
not(3) returns the bitwise Boolean inverse of i. This is also known as the “Bitwise complement” or “Logical negation” of the value.
If an input bit is a one, that position is a zero on output. Conversely any input bit that is zero is a one on output.
Options#
- i
The value to flip the bits of.
Result#
The result has the value obtained by complementing i bit-by-bit according to the following truth table:
> I | NOT(I)
> ----#----------
> 1 | 0
> 0 | 1
That is, every input bit is flipped.
Examples#
Sample program
program demo_not
implicit none
integer :: i
! basics
i=-13741
print *,'the input value',i,'represented in bits is'
write(*,'(1x,b32.32,1x,i0)') i, i
i=not(i)
print *,'on output it is',i
write(*,'(1x,b32.32,1x,i0)') i, i
print *, " on a two's complement machine flip the bits and add 1"
print *, " to get the value with the sign changed, for example."
print *, 1234, not(1234)+1
print *, -1234, not(-1234)+1
print *, " of course 'x=-x' works just fine and more generally."
end program demo_not
Results:
the input value -13741 represented in bits is
11111111111111111100101001010011 -13741
on output it is 13740
00000000000000000011010110101100 13740
on a two's complement machine flip the bits and add 1
to get the value with the sign changed, for example.
1234 -1234
-1234 1234
of course 'x=-x' works just fine and more generally.
Standard#
Fortran 95
See Also#
iand(3), ior(3), ieor(3), ibits(3), ibset(3),
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ishftc#
Name#
ishftc(3) - [BIT:SHIFT] Shift rightmost bits circularly, AKA. a logical shift
Synopsis#
result = ishftc( i, shift [,size] )
elemental integer(kind=KIND) function ishftc(i, shift, size)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: shift
integer(kind=**),intent(in),optional :: size
Characteristics#
a kind designated as ** may be any supported kind for the type
i may be an integer of any kind
shift and size may be integers of any kind
the kind for i dictates the kind of the returned value.
Description#
ishftc(3) circularly shifts just the specified rightmost bits of an integer.
ishftc(3) returns a value corresponding to i with the rightmost size bits shifted circularly shift places; that is, bits shifted out one end of the section are shifted into the opposite end of the section.
A value of shift greater than zero corresponds to a left shift, a value of zero corresponds to no shift, and a value less than zero corresponds to a right shift.
Options#
- i
The value specifying the pattern of bits to shift
- shift
If shift is positive, the shift is to the left; if shift is negative, the shift is to the right; and if shift is zero, no shift is performed.
The absolute value of shift must be less than size (simply put, the number of positions to shift must be less than or equal to the number of bits specified to be shifted).
- size
The value must be greater than zero and less than or equal to bit_size(i).
The default if bit_size(i) is absent is to circularly shift the entire value i.
Result#
The result characteristics (kind, shape, size, rank, …) are the same as i.
The result has the value obtained by shifting the size rightmost bits of i circularly by shift positions.
No bits are lost.
The unshifted bits are unaltered.
Examples#
Sample program:
program demo_ishftc
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: i
character(len=*),parameter :: g='(b32.32,1x,i0)'
! basics
write(*,*) ishftc(3, 1),' <== typically should have the value 6'
print *, 'lets start with this:'
write(*,'(b32.32)')huge(0)
print *, 'shift the value by various amounts, negative and positive'
do i= -bit_size(0), bit_size(0), 8
write(*,g) ishftc(huge(0),i), i
enddo
print *,'elemental'
i=huge(0)
write(*,*)ishftc(i,[2,3,4,5])
write(*,*)ishftc([2**1,2**3,-2**7],3)
print *,'note the arrays have to conform when elemental'
write(*,*)ishftc([2**1,2**3,-2**7],[5,20,0])
end program demo_ishftc
Results:
> 6 <== typically should have the value 6
> lets start with this:
> 01111111111111111111111111111111
> shift the value by various amounts, negative and positive
> 01111111111111111111111111111111 -32
> 11111111111111111111111101111111 -24
> 11111111111111110111111111111111 -16
> 11111111011111111111111111111111 -8
> 01111111111111111111111111111111 0
> 11111111111111111111111101111111 8
> 11111111111111110111111111111111 16
> 11111111011111111111111111111111 24
> 01111111111111111111111111111111 32
> elemental
> -3 -5 -9 -17
> 16 64 -1017
> note the arrays have to conform when elemental
> 64 8388608 -128
Standard#
Fortran 95
See Also#
ishft(3) - Logical shift of bits in an integer
shifta(3) - Right shift with fill
shiftl(3) - Shift bits left
shiftr(3) - Combined right shift of the bits of two int…
dshiftl(3) - Combined left shift of the bits of two inte…
dshiftr(3) - Combined right shift of the bits of two int…
cshift(3) - Circular shift elements of an array
eoshift(3) - End-off shift elements of an array
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
ishft#
Name#
ishft(3) - [BIT:SHIFT] Logical shift of bits in an integer
Synopsis#
result = ishftc( i, shift )
elemental integer(kind=KIND) function ishft(i, shift )
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: shift
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer of any kind. the kind for i dictates the kind of the returned value.
shift is an integer of any kind.
Description#
ishft(3) returns a value corresponding to i with all of the bits shifted shift places left or right as specified by the sign and magnitude of shift.
Bits shifted out from the left end or right end are lost; zeros are shifted in from the opposite end.
Options#
- i
The value specifying the pattern of bits to shift
- shift
A value of shift greater than zero corresponds to a left shift, a value of zero corresponds to no shift, and a value less than zero corresponds to a right shift.
If the absolute value of shift is greater than bit_size(i), the value is undefined.
Result#
The result has the value obtained by shifting the bits of i by shift positions.
If shift is positive, the shift is to the left
if shift is negative, the shift is to the right
if shift is zero, no shift is performed.
Bits shifted out from the left or from the right, as appropriate, are lost. Zeros are shifted in from the opposite end.
Examples#
Sample program:
program demo_ishft
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: shift
character(len=*),parameter :: g='(b32.32,1x,i0)'
write(*,*) ishft(3, 1),' <== typically should have the value 6'
shift=4
write(*,g) ishft(huge(0),shift), shift
shift=0
write(*,g) ishft(huge(0),shift), shift
shift=-4
write(*,g) ishft(huge(0),shift), shift
end program demo_ishft
Results:
> 6 <== typically should have the value 6
> 11111111111111111111111111110000 4
> 01111111111111111111111111111111 0
> 00000111111111111111111111111111 -4
Standard#
Fortran 95
See Also#
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
shifta#
Name#
shifta(3) - [BIT:SHIFT] Right shift with fill
Synopsis#
result = shifta(i, shift )
elemental integer(kind=KIND) function shifta(i, shift)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: shift
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer of any kind
shift is an integer of any kind
the result will automatically be of the same type, kind and rank as i.
Description#
shifta(3) returns a value corresponding to i with all of the bits shifted right by shift places and the vacated bits on the left filled with the value of the original left-most bit.
Options#
- i
The initial value to shift and fill
- shift
how many bits to shift right. It shall be nonnegative and less than or equal to bit_size(i). or the value is undefined. If shift is zero the result is i.
Result#
The result has the value obtained by shifting the bits of i to the right shift bits and replicating the leftmost bit of i in the left shift bits (Note the leftmost bit in “two’s complement” representation is the sign bit).
Bits shifted out from the right end are lost.
If shift is zero the result is i.
Examples#
Sample program:
program demo_shifta
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer(kind=int32) :: ival
integer :: shift
integer(kind=int32) :: oval
integer(kind=int32),allocatable :: ivals(:)
integer :: i
integer(kind=int8) :: arr(2,2)=reshape([2,4,8,16],[2,2])
! basic usage
write(*,*)shifta(100,3)
! loop through some interesting values
shift=5
ivals=[ -1, -0, +0, +1, &
& int(b"01010101010101010101010101010101"), &
& int(b"10101010101010101010101010101010"), &
& int(b"00000000000000000000000000011111") ]
! does your platform distinguish between +0 and -0?
! note the original leftmost bit is used to fill in the vacated bits
write(*,'(/,"SHIFT = ",i0)') shift
do i=1,size(ivals)
ival=ivals(i)
write(*,'( "I = ",b32.32," == ",i0)') ival,ival
oval=shifta(ival,shift)
write(*,'( "RESULT = ",b32.32," == ",i0)') oval,oval
enddo
! elemental
write(*,*)"characteristics of the result are the same as input"
write(*,'(*(g0,1x))') &
& "kind=",kind(shifta(arr,3)), "shape=",shape(shifta(arr,3)), &
& "size=",size(shifta(arr,3)) !, "rank=",rank(shifta(arr,3))
end program demo_shifta
Results:
> 12
>
> SHIFT = 5
> I = 11111111111111111111111111111111 == -1
> RESULT = 11111111111111111111111111111111 == -1
> I = 00000000000000000000000000000000 == 0
> RESULT = 00000000000000000000000000000000 == 0
> I = 00000000000000000000000000000000 == 0
> RESULT = 00000000000000000000000000000000 == 0
> I = 00000000000000000000000000000001 == 1
> RESULT = 00000000000000000000000000000000 == 0
> I = 01010101010101010101010101010101 == 1431655765
> RESULT = 00000010101010101010101010101010 == 44739242
> I = 10101010101010101010101010101010 == -1431655766
> RESULT = 11111101010101010101010101010101 == -44739243
> I = 00000000000000000000000000011111 == 31
> RESULT = 00000000000000000000000000000000 == 0
> characteristics of the result are the same as input
> kind= 1 shape= 2 2 size= 4
Standard#
Fortran 2008
See Also#
shiftl(3), shiftr(3), ishft(3), ishftc(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
shiftl#
Name#
shiftl(3) - [BIT:SHIFT] Shift bits left
Synopsis#
result = shiftl( i, shift )
elemental integer(kind=KIND) function shiftl(i, shift)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: shift
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer of any kind
shift is an integer of any kind
the result will automatically be of the same type, kind and rank as i.
Description#
shiftl(3) returns a value corresponding to i with all of the bits shifted left by shift places.
Bits shifted out from the left end are lost, and bits shifted in from the right end are set to 0.
If the absolute value of shift is greater than bit_size(i), the value is undefined.
For example, for a 16-bit integer left-shifted five …
> |a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p| <- original 16-bit example
> |f|g|h|i|j|k|l|m|n|o|p| <- left-shifted five
> |f|g|h|i|j|k|l|m|n|o|p|0|0|0|0|0| <- right-padded with zeros
Note the value of the result is the same as ishft (i, shift).
Options#
- i
The initial value to shift and fill in with zeros
- shift
how many bits to shift left. It shall be nonnegative and less than or equal to bit_size(i).
Result#
The return value is of type integer and of the same kind as i.
Examples#
Sample program:
program demo_shiftl
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: shift
integer(kind=int32) :: oval
integer(kind=int32) :: ival
integer(kind=int32),allocatable :: ivals(:)
integer :: i
print *, ' basic usage'
ival=100
write(*,*)ival, shiftl(ival,3)
! elemental (input values may be conformant arrays)
print *, ' elemental'
! loop through some ivalues
shift=9
ivals=[ &
& int(b"01010101010101010101010101010101"), &
& int(b"10101010101010101010101010101010"), &
& int(b"11111111111111111111111111111111") ]
write(*,'(/,"SHIFT = ",i0)') shift
do i=1,size(ivals)
! print initial value as binary and decimal
write(*,'( "I = ",b32.32," == ",i0)') ivals(i),ivals(i)
! print shifted value as binary and decimal
oval=shiftl(ivals(i),shift)
write(*,'( "RESULT = ",b32.32," == ",i0)') oval,oval
enddo
! more about elemental
ELEM : block
integer(kind=int8) :: arr(2,2)=reshape([2,4,8,16],[2,2])
write(*,*)"characteristics of the result are the same as input"
write(*,'(*(g0,1x))') &
& "kind=",kind(shiftl(arr,3)), "shape=",shape(shiftl(arr,3)), &
& "size=",size(shiftl(arr,3)) !, "rank=",rank(shiftl(arr,3))
endblock ELEM
end program demo_shiftl
Results:
> basic usage
> 100 800
> elemental
>
> SHIFT = 9
> I = 01010101010101010101010101010101 == 1431655765
> RESULT = 10101010101010101010101000000000 == -1431655936
> I = 10101010101010101010101010101010 == -1431655766
> RESULT = 01010101010101010101010000000000 == 1431655424
> I = 11111111111111111111111111111111 == -1
> RESULT = 11111111111111111111111000000000 == -512
> characteristics of the result are the same as input
> kind= 1 shape= 2 2 size= 4
Standard#
Fortran 2008
See Also#
shifta(3), shiftr(3), ishft(3), ishftc(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost
shiftr#
Name#
shiftr(3) - [BIT:SHIFT] Shift bits right
Synopsis#
result = shiftr( i, shift )
elemental integer(kind=KIND) function shiftr(i, shift)
integer(kind=KIND),intent(in) :: i
integer(kind=**),intent(in) :: shift
Characteristics#
a kind designated as ** may be any supported kind for the type
i is an integer of any kind
shift is an integer of any kind
the result will automatically be of the same type, kind and rank as i.
Description#
shiftr(3) returns a value corresponding to i with all of the bits shifted right by shift places.
If the absolute value of shift is greater than bit_size(i), the value is undefined.
Bits shifted out from the right end are lost, and bits shifted in from the left end are set to 0.
For example, for a 16-bit integer right-shifted five …
> |a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p| <- original 16-bit example
> |a|b|c|d|e|f|g|h|i|j|k| <- right-shifted five
> |0|0|0|0|0|f|g|h|i|j|k|l|m|n|o|p| <- left-padded with zeros
Note the value of the result is the same as ishft (i, -shift).
Options#
- i
The value to shift
- shift
How many bits to shift right. It shall be nonnegative and less than or equal to bit_size(i).
Result#
The remaining bits shifted right shift positions. Vacated positions on the left are filled with zeros.
Examples#
Sample program:
program demo_shiftr
use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64
implicit none
integer :: shift
integer(kind=int32) :: oval
integer(kind=int32) :: ival
integer(kind=int32),allocatable :: ivals(:)
integer :: i
print *,' basic usage'
ival=100
write(*,*)ival, shiftr(100,3)
! elemental (input values may be conformant arrays)
print *,' elemental'
shift=9
ivals=[ &
& int(b"01010101010101010101010101010101"), &
& int(b"10101010101010101010101010101010"), &
& int(b"11111111111111111111111111111111") ]
write(*,'(/,"SHIFT = ",i0)') shift
do i=1,size(ivals)
! print initial value as binary and decimal
write(*,'( "I = ",b32.32," == ",i0)') ivals(i),ivals(i)
! print shifted value as binary and decimal
oval=shiftr(ivals(i),shift)
write(*,'( "RESULT = ",b32.32," == ",i0,/)') oval,oval
enddo
! more on elemental
ELEM : block
integer(kind=int8) :: arr(2,2)=reshape([2,4,8,16],[2,2])
write(*,*)"characteristics of the result are the same as input"
write(*,'(*(g0,1x))') &
& "kind=",kind(shiftr(arr,3)), "shape=",shape(shiftr(arr,3)), &
& "size=",size(shiftr(arr,3)) !, "rank=",rank(shiftr(arr,3))
endblock ELEM
end program demo_shiftr
Results:
> basic usage
> 100 12
> elemental
>
> SHIFT = 9
> I = 01010101010101010101010101010101 == 1431655765
> RESULT = 00000000001010101010101010101010 == 2796202
>
> I = 10101010101010101010101010101010 == -1431655766
> RESULT = 00000000010101010101010101010101 == 5592405
>
> I = 11111111111111111111111111111111 == -1
> RESULT = 00000000011111111111111111111111 == 8388607
>
> characteristics of the result are the same as input
> kind= 1 shape= 2 2 size= 4
Standard#
Fortran 2008
See Also#
shifta(3), shiftl(3), ishft(3), ishftc(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost