I’ve been updating my old programs to use the MATH unit in freepascal and while
testing things I came across a runtime error 217 Invalid floating point
operation. Here is my test program
Uses math;
var
variable1:double;
variable2:double;
Begin
variable1:= Infinity;
variable2:= -1*Infinity;
Writeln(variable1,' ',Variable2,' ',Variable1+Variable2);
End.
My output is:
Running "i:\programming\test\testmath.exe "
An unhandled exception occurred at $004015F6:
EInvalidOp: Invalid floating point operation
$004015F6 main, line 8 of i:/programming/test/testmath.pas
+Inf -Inf
According to the link here: https://en.wikipedia.org/wiki/NaN
NaN should be produced:
The additions (+∞) + (−∞), (−∞) + (+∞) and equivalent subtractions (+∞) − (+∞)
and (−∞) − (−∞).
I can do things like +infinity*2 and +infinity-3 and even sqr(infinity) and
power(infinity,10) the results are still +Inf which is expected… but I can’t
do anything involving subtracting infinity from infinity. Here is another test
program that illustrates this more clearly:
Uses math;
var
variable1:double;
variable2:double;
Begin
variable1:= 1/0;
variable2:= -1/0;
Writeln(' V1',variable1);
Writeln(' V2',variable2);
Writeln(' SQRT(-1)',Sqrt(-1));
Writeln(' V1*V1',variable1*variable1);
Writeln(' V1*V2',variable1*variable2);
Writeln(' V1+3',variable1+3);
Writeln(' V1+V1',variable1+variable1);
Writeln(' V1-3',variable1-3);
Writeln(' Sqr(V1)',Sqr(Variable1));
Writeln(' Sqr(V2)',Sqr(Variable2));
Writeln(' Sqrt(-1)',Sqrt(-1));
Writeln(' Sqrt(V1)',Sqrt(Variable1));
Writeln('Power(V1,10)',Power(Variable1,10));
Writeln(' ABS(V2)',ABS(Variable2));
Writeln(' Sqrt(-1*V1)',Sqrt(-1*Variable1));//runtime error 217 Should be NAN
Writeln(' Sqrt(V2)',Sqrt(Variable2)); //runtime error 217 Should be NAN
Writeln(' V1-V1',variable1-variable1); //runtime error 217 Should be NAN
Writeln(' V1+V2',variable1+variable2); //runtime error 217 Should be NAN
End.
Running "i:\programming\test\testmath.exe "
V1 +Inf
V2 -Inf
SQRT(-1) Nan
V1*V1 +Inf
V1*V2 -Inf
V1+3 +Inf
V1+V1 +Inf
V1-3 +Inf
Sqr(V1) +Inf
Sqr(V2) +Inf
Sqrt(-1) Nan
Sqrt(V1) +Inf
Power(V1,10) +Inf
ABS(V2) +Inf
An unhandled exception occurred at $00401A43:
EInvalidOp: Invalid floating point operation
$00401A43 main, line 22 of I:/Programming/Test/testmath.pas
Sqrt(-1*V1)
It seems to me that the whole purpose of +Inf, -Inf, and NaN was so you could
evaluate complex formulas and NOT get a runtime error… Is this behavior just a
bug that should be reported? Testing was done with V3.0.4
James
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