Have you tried using the Pascal Str() function like so:
var
num: Integer;
text: String;
begin
num := 123;
Str(num, text); { text now contains '123' }
Writeln(text);
end.
-----Original Message-----
From: fpc-pascal <[email protected]> On Behalf Of Mark
via fpc-pascal
Sent: Monday, September 21, 2026 11:31 AM
To: [email protected]
Cc: Mark <[email protected]>
Subject: [fpc-pascal] Formatting negative zero floating point numbers
I have a free pascal and a C program that both generate numeric output in
text format. I expect both programs to produce the same output and I
automatically verify that with a simple textual diff in my build process.
That works fine in general except for negative zero floating point values
(https://en.wikipedia.org/wiki/Signed_zero). The issue is that FloatToStrF
does not output a minus sign for those values. Here are short examples to
reproduce the behavior. The C output is what I would expect.
C:
#include <stdio.h>
int main() {
double d = -0.0;
printf("%e\n", d);
return 0;
}
$ ./main
-0.000000e+00
Pascal (fpc-3.2.2):
program main;
uses
sysutils;
var
d :Double;
s :String;
begin
d := -0.0;
Writeln(d);
WriteStr(s, d);
Writeln(s);
Str(d:0:17, s);
Writeln(s);
Writeln(FloatToStrF(d, ffExponent, 17, 3));
Writeln(Format('%e', [d]));
end.
$ ./main
-0.0000000000000000E+000
-0.0000000000000000E+000
-0.00000000000000000
0.0000000000000000E+000
0.0000000000000000E+000
The output of FloatToStrF and Format is different to what I expect and get
with C. However, it is also different to what Write/WriteStr/Str produces
which seems inconsistent to me. Is that actually the expected behavior? If
yes, is there another way to get the desired output? Using WriteStr is no
alternative for my use case, since I need control over the number of digits
for the exponent.
Thanks,
Mark
_______________________________________________
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_______________________________________________
fpc-pascal maillist - [email protected]
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
