The IFDEF macro tests for the logical true value of the argument in its first parameter list. If `true', the second parameter list is evaluated, else, the third parameter list is evaluated. All three parameter lists (the variable, the true-list and the false-list) must be present; though the true-list and/or the false-list may be empty parameter lists. The variable in the first parameter list evaluates the macro to `true' when the first argument is:
  • a built-in macro,
  • a user-defined macro (see DEFINEMACRO, section ??),
  • a logical symbol (see DEFINESYMBOL, section ??),
  • a counter (see NEWCOUNTER, section ??).
  • For an example, see the description of DEFINESYMBOL, section ??.
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    Copyright (c) 1997, 1998, 1999 Karel Kubat and Jan Nieuwenhuizen.

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