Microsoft KB Archive/70420

Wrong < or > Boolean Result Using Real Function As 2nd Operand PSS ID Number: Q70420 Article last modified on 04-03-1991 PSS database name: S_QuickPas

1.00

MS-DOS

Summary:

When a function that returns a floating-point value is used as an operand on the right-hand side of a relational expression using “>” or “<”, the resulting boolean value may be incorrect.

Microsoft has confirmed this to be a problem with Microsoft QuickPascal version 1.00 for MS-DOS. We are researching this problem and will post new information here as it becomes available.

More Information:

The following sample code demonstrates the problem:

    function test: real;   {returns value of 3}
       begin
          test := 3;
       end;

    begin

       {function as 2nd operand - results can be incorrect}
       if 2>test then writeln ('This IF is incorrectly shown TRUE.');
       writeln (2>test);     {'TRUE'   incorrect}
       writeln (3=test);     {'TRUE'   correct}
       writeln (4>test);     {'FALSE'  incorrect}
       writeln (2<test);     {'FALSE'  incorrect}
       writeln (4<test);     {'TRUE'   incorrect}

       {function as first operand - results correct}
       writeln (test>2);     {'TRUE'   correct}
       writeln (test=3);     {'TRUE'   correct}
       writeln (test>4);     {'FALSE'  correct}
       writeln (test<2);     {'FALSE'  correct}
       writeln (test<4);     {'TRUE'   correct}

    end.

This problem occurs only if the value returned by the function is a floating-point value. If the value returned by the function is an integer type, then no problems occur.

As a workaround to this problem, if the returned value of the function must be used as the second operand in the expression, then put the returned value of the function into a variable and use that variable in the expression.

    x := test
    writeln (4 > x);    {'TRUE'   correct}

Copyright Microsoft Corporation 1991.