$LANGUAGE_NUM: Number of current language ¶‘$LANGUAGE_NUM’ expands to an integer that uniquely defines the current language, as follows:
Language $LANGUAGE_NUMC 0C++ 1Fortran 2Fortran-90 3Ratfor 4Ratfor-90 5TeX 6VERBATIM 7
This built-in is useful in conjunction with an $IFCASE
construction; see $IFCASE: n-way conditional.