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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

  ◄Scoping Rules►   ◄Scoping Rules: DEF FN Functions►   ◄Contents►   ◄Index►
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DEF FN Functions
 
The DEF FN is an exception to the BASIC scoping rules. Every variable in a
DEF FN function that isn't in its parameter list is part of the module-
level code. In order to make a variable local to a DEF FN, you must declare
the variable in a STATIC statement. The STATIC statement in the following
DEF FN function makes the variable I local:
 
  CONST NO = 0, YES = NOT NO
  DEF FNIsThereAZ (A$)
  STATIC I
    FOR I = 1 TO LEN(A$)
     IF UCASE$(MID$(A$, I, 1)) = "Z" THEN
        FNIsThereAZ = YES
        EXIT DEF
      END IF
    NEXT I
    FNIsThereAZ = NO
  END DEF
 
Remember, as a general rule, a FUNCTION is preferred over a DEF FN because
of its improved portability, increased modularity, and more structured
programming style.