Q38495: "Subscript Out of Range" Using Complex Expression with BC /D

Article: Q38495
Product(s): See article
Version(s): 4.00 4.00b
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b fixlist4.50 B_BasicCom | mspl13_basic
Last Modified: 16-DEC-1989

The program below returns a "Subscript Out Of Range" error message at
run time when compiled with the BC /D (debug) option. The program
works correctly inside the QB.EXE editor.

Microsoft has confirmed this to be a problem in Microsoft QuickBASIC
Versions 4.00 and 4.00b and in Microsoft BASIC Compiler Versions 6.00
and 6.00b for MS-DOS and MS OS/2 (buglist6.00, buglist6.00b). This
problem was corrected in QuickBASIC Version 4.50 and in Microsoft
BASIC PDS Version 7.00 (fixlist7.00).

To work around the problem, you can break up the complex expression.
For example, replace the following line:

        r = SGN(t(b%)) * SQR(ABS(t(b%)))

with the following:

        r1 = t(b%)
        r2 = ABS(r1)
        r = SGN(r1) * SQR(r2)

The following is a code example:

DIM t(12)
FOR i = -6 TO 6
  t(i + 6) = i
NEXT i
FOR b% = 1 TO 12
  r = SGN(t(b%)) * SQR(ABS(t(b%)))
  PRINT r
NEXT b%

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