Re: Lua multiplication problem
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- Subject: Re: Lua multiplication problem
- From: Adrian Sietsma <adrian_groups@...>
- Date: 2005年11月25日 19:23:39 +1100
Tom Reahard wrote:
I am experiencing some strange behavior with numbers where the results
of a multiplication should equal a given number but Lua does not
recognize the equality.
it appears to be a floating-point issue :
Lua 5.0.2 Copyright (C) 1994-2004 Tecgraf, PUC-Rio
> print ( 20425 * .053, 1082.525, 1082.525-(20425*0.053) )
1082.525 1082.525 2.2737367544323e-013
> print ( 20.425 * 53, 1082.525,1082.525-(20.425*53) )
1082.525 1082.525 0
note how the integer multiply works ok!
this is _not_ a lua issue - try the following in c++ :
double d1 = 20425.0;
double d2 = 0.053;
double d3 = 1082.525;
double d4 = d1 * d2;
double d5 = d3 - d4;
d5 == 2.27x10-13 also !
it will have something to do with the binary representation of one of the
doubles, i guess...
Adrian