[geeks] expr and math

[Phil Stracchino]

On Tue, Sep 21, 2004 at 04:00:48AM -0500, Brian Dunbar wrote:
> I need to do a bit of math on some data in ascii format.  Hey, sez I, 
> the expr function can handle that.  The results was getting strange on 
> me, however .. what's going on here?
> 
> briandunbar_natasha_~:expr 90 \* 100
> 9000
> briandunbar_natasha_~:expr 90 \* 1000
> 90000
> briandunbar_natasha_~:expr 90 \* 10000
> 900000
> briandunbar_natasha_~:expr 90 \* 100000
> 9000000
> briandunbar_natasha_~:expr 90 \* 1000000
> 90000000
> briandunbar_natasha_~:expr 90 \* 10000000
> 900000000
> briandunbar_natasha_~:expr 90 \* 100000000
> 410065408
> briandunbar_natasha_~:expr 90 \* 1000000000
> -194313216
> 
> I barely escaped Rube Junction High School with a C average, but even I 
> know in the real world 90 X 100000000 isn't '410065408'
> 
> What gives?


I'd guess an integer overflow problem somewhere inside expr.  Tried
piping it to bc instead?

babylon5:alaric:~:3 $ echo 90 \* 1000000000 |bc
90000000000


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