Is this the FORTRAN logical value true? F77_ISTRUE
| Solaris: | ( var ) |
| OSF/1: | ( (var)&1 ) |
| VAX/VMS: | ( (var)&1 ) |
The VAX FORTRAN and DEC FORTRAN for RISC compilers only use the lowest bit for the logical flag. Hence 0 = false, 1 = true, 2 = false, 3 = true, etc.
The Sun FORTRAN compiler uses zero = false, non zero = true.
The FORTRAN for RISC compiler (from MIPS) on the DECstation uses zero = false, non zero = true. This means that the correct value of this C macro depends on which FORTRAN compiler is being used.