GAWK adding big numbers wrong

[Bernd Schueller]

Hello,

When calculating _big_ numbers with 'gawk' I get wrong results with
numbers larger than 53 bits (dec. > 9007199254740991)!

The program:
---
gawk -v sum=1 '
BEGIN {
 for (i=1 ; i<57; i++)
 {printf("bit: %d\tvalue: %.f\tsum of %d bits:\t%.f\n" , i, sum, i,
summe+=sum) ; sum=sum*2}
 }
'
---

generates:
...
bit: 52 value: 2251799813685248 sum of 52 bits: 4503599627370495
bit: 53 value: 4503599627370496 sum of 53 bits: 9007199254740991
bit: 54 value: 9007199254740992 sum of 54 bits: 18014398509481984 *WRONG*
bit: 55 value: 18014398509481984        sum of 55 bits: 36028797018963968
...

The program:
---
gawk ' BEGIN { for (i=9007199254740988 ; i<9007199254740994 ; i++) printf
"%.f\n",i } '
---

results in an infinite loop, continiously printing: 9007199254740992.


I am using 'GNU Awk 3.0.4' from the 'Cygwin Package' on a Windows system:

Package             Version
bash                2.05a-3
gawk                3.0.4-1

System is:
Microsoft Windows 98 4.10.2222 A
GenuineIntel x86 Family 6 Model 8 Stepping 6 (Celeron 700MHz)
FPU built-in


I do not suggest a CPU/FPU or Win98 problem, as I can add up the numbers
correctly using the calculator tool from the Win98 menue...?!


Thank you!

Best regards
 bs
--
Bernhard Schueller
Tilsiter Weg 4
D-68723 Schwetzingen
mailto:address@hidden