7.2.3.49 $PP: The C preprocessor symbol

$PP is shorthand for ‘$UNSTRING($P)’ (see $P), or (essentially) a synonym for ‘$UNSTRING("#")’ (see $UNSTRING). It is useful, particularly in FORTRAN, for constructing FWEB macro definitions that expand to C preprocessor statements. For an example, see $P. For a detailed discussion of the difference between ‘$P’ and ‘$PP’, see Strings and quotes.