Manual Reference Pages - merge_bits (3fortran)

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

o 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

o I : value to select bits from when the associated bit in the mask is

1.

o J : value to select bits from when the associated bit in the mask is

0.

o 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

Manual Reference Pages - merge_bits (3fortran)

NAME

SYNOPSIS

CHARACTERISTICS

DESCRIPTION

OPTIONS

RESULT

EXAMPLES

STANDARD

SEE ALSO