F77_ISTRUE - Is this the FORTRAN logical value true?

Description:

Does the argument of the macro evaluate to a value that FORTRAN would treat as a LOGICAL true?

Invocation:

if( F77_ISTRUE(var) ) ...

Arguments:

var

The name of the value to be tested.

Examples:

F77_ISTRUE(var)

will expand as follows:

Solaris:	( var )
OSF/1:	( (var)&1 )
VAX/VMS:	( (var)&1 )

Notes:

• 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.