Re^2: float values and operators

Hi Zaxo,

I noticed that this doesn't happen in C ...

bash-2.05b$ cat float.c
#include <stdio.h>
 
int main () {
        float a = 36.8;
        float b = 36.6;
        if( a >= ( b + 0.2 ) ) { printf ("true\n"); }
}
bash-2.05b$ gcc -o float float.c
bash-2.05b$ ./float
true
[download]

... and does happen in Python ...

bash-2.05b$ cat float.py
#!/usr/bin/python
A = 36.8
B = 36.6
if( A >= B + 0.2 ):
        print "true"
else:
        print "false"
bash-2.05b$ ./float.py
false
[download]

I would of included a java example but I aint got all day to download the SDK. Maybe I'll update with one later. Can you explain why C deals with float point number while Perl and Python appear to have this problem? Is it a compiled verses and interpreted language issue?

Thanks

Plankton: 1% Evil, 99% Hot Gas.

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Re^3: float values and operators by Aristotle (Chancellor) on Aug 11, 2004 at 21:43 UTC
Are you sure C "deals"? `$ cat imprec.c #include <stdio.h> int main () { float fa = 36.8; float fb = 36.6; double da = 36.8; double db = 36.6; printf( ( fa >= ( fb + 0.2 ) ) ? "true\n" : "false\n" ); printf( ( da >= ( db + 0.2 ) ) ? "true\n" : "false\n" ); } $ gcc -o imprec imprec.c $ ./imprec true false` [download] You're seeing the result of cut-off caused by `float`'s lower precision. Perl and Python use `double`s in all floating point operations. Makeshifts last the longest.	[reply] [d/l]
Re^3: float values and operators by ikegami (Patriarch) on Aug 11, 2004 at 21:49 UTC
C doesn't deal, actually: `$ cat a.c #include <stdio.h> int main() { printf("%s\n", 36.6 == 36.8-0.2 ? "true" : "false"); return 0; } $ gcc a.c $ a.out false` [download]	[reply] [d/l]