Q59008: Bad Integer Output Using DEF FN, VAL, FOR-NEXT in BASIC 7.00

Article: Q59008
Product(s): See article
Version(s): 7.00   | 7.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | SR# S900217-5 buglist7.00 fixlist7.10 | mspl13_basic
Last Modified: 1-AUG-1990

When run as an .EXE program (compiled with BC.EXE), the program below
gives incorrect output in Microsoft BASIC Professional Development
System (PDS) version 7.00 for MS-DOS and MS OS/2. The same program
gives correct output when run in the QBX.EXE environment or compiled
with the BC /D option.

The program fails when it assigns an integer array (which is
subscripted by a FOR...NEXT loop counter) to the VAL of a DEF FN
string function operating on a temporary string that was assigned to
an array element that is subscripted by the FOR...NEXT loop counter.

Microsoft has confirmed this to be a problem in Microsoft BASIC
Professional Development System (PDS) version 7.00. This problem was
corrected in BASIC PDS version 7.10.

This problem does not occur with an .EXE compiled in QuickBASIC
version 4.50 or earlier.

The program below outputs "2 2" instead of "1 2" from an .EXE program.
(The problem occurs whether compiled as a stand-alone .EXE or as an
.EXE requiring the BRT module). This problem is corrected by doing any
one of the following:

1. Compiling with the BC /D option.

2. Removing the DEFINT A-Z line.

3. Replacing n (the ending value of the FOR...NEXT loop counter) with
   the constant 2 in the FOR...NEXT statement.

4. Eliminating the use of the temporary (placeholder) variable t$ by
   putting s$(i) in place of it in the VAL function.

5. Replacing d(i) with a nonarray (scalar) variable.

Code Example
------------

   DEFINT A-Z
   DIM s$(1 TO 2), d(1 TO 2)
   DEF FNa$ (x$)
   FNa$ = x$
   END DEF
   CLS
   n = 2
   s$(1) = "1"
   s$(2) = "2"
   PRINT
   FOR i = 1 TO n
      t$ = s$(i)
      d(i) = VAL(FNa$(t$))
   ' One workaround is to use:   d(i) = VAL(FNa$(s$(i)))
      PRINT d(i);
   NEXT
   END

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