Q51292: PRINT SPC(n) USING on Array Element, Bad Results

Article: Q51292
Product(s): See article
Version(s): 4.00 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S891110-96 buglist4.00 buglist4.50 fixlist4.00b | mspl13_basic
Last Modified: 13-DEC-1989

The following code example demonstrates that using the SPC(n) function
with the PRINT USING statement on an element of an array ($DYNAMIC or
$STATIC) produces incorrect results with BC.EXE compiler Versions 4.00
and 4.50. This problem does not occur in BC.EXE provided with
QuickBASIC 4.00b or with the BASIC compiler 6.00 or 6.00b. This
problem does not occur in the QB.EXE 4.00, 4.00b, and 4.50 editors.
This problem does not occur in BC.EXE or QBX.EXE provided with
Microsoft BASIC PDS Version 7.00 (fixlist7.00).

The code example produces incorrect output when compiled with BC.EXE
Version 4.50. Compiled with BC.EXE Version 4.00, it produces the error
"Type mismatch in line 40 of module <filename> at address xxxx:xxxx".

This problem occurs with either dynamic or static arrays. Compiling
with the /AH switch does NOT correct the problem in either Version
4.00 or 4.50.

There are several workarounds to this problem. The easiest workaround
is to use a literal such as " " or to use a function such as
STRING(n, " "), which produces the same results as using the SPC(n)
function. For example,

    PRINT ; STRING$(1, " ") ; USING ........

is the equivalent of

    PRINT ; SPC(1) ; USING .......

The above workaround will work in Version 4.00 or 4.50. However, in
Version 4.50 the problem also does not occur if you compile with
either the /d or /x options as follows:

1. In the QB.EXE editor, choose to "Produce Debug Code".

2. On the BC.EXE compile line use /D.

The problem also does not occur if you use error trapping. This is
done by including an ON ERROR GOTO and RESUME in the program. On the
BC.EXE command line, include the /X compiler option. No combination of
compiler switches corrects the problem for Version 4.00.

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

' This code example can be used to reproduce the problem.
' Do not include error trapping or produce debug code.
REM $DYNAMIC
CLS
DEFINT A-Z
TYPE Rec1
       F1 AS STRING * 15
       F2 AS INTEGER
       F3 AS INTEGER
       F4 AS INTEGER
       F5 AS INTEGER
       F6 AS INTEGER
       F7 AS INTEGER
       F8 AS INTEGER
END TYPE
DIM a1(2) AS Rec1
FOR k = 1 TO 2
       READ a1(k).F1
       READ a1(k).F2
       READ a1(k).F3
       READ a1(k).F4
       READ a1(k).F5
       READ a1(k).F6
       READ a1(k).F8
       a1(k).F7 = a1(k).F5 - a1(k).F6
NEXT k
Col = 12
LOCATE , Col
PRINT "  PGM=M1   A           B   C   D   E    F     G    H    J"
LOCATE , Col
PRINT STRING$(60, 196)
10 FOR k = 1 TO 2
20     LOCATE , Col
30     PRINT SPC(1); USING "###"; k;
40     PRINT ".";
50     PRINT ; a1(k).F1;
60     PRINT ; SPC(1); USING "###"; a1(k).F2 + a1(k).F3 + a1(k).F4;
70     PRINT ; SPC(1); USING "###"; a1(k).F2;
80
'********************************************************************
90      PRINT ; SPC(1); USING "###"; a1(k).F3; ' Error occurs here.
100     PRINT ; SPC(1); USING "###"; a1(k).F4; ' Error occurs here.
110
120
'********************************************************************
130     PRINT ; SPC(1); USING "####"; a1(k).F5;
140     PRINT " :";
150      PRINT ; SPC(1); USING "###"; a1(k).F6;
160     PRINT ; SPC(1); USING "####"; a1(k).F7;
170     PRINT ; SPC(1); USING "####"; a1(k).F8
180 NEXT k
190 END

DATA "Club 01   ",  2, 0, 9, 33, 57,  4
DATA "Club 02   ",  3, 2, 6, 45, 17,  4
END

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