Re: exponent and modulus operator oddities on ppc

[Glenn McAllister <glenn@...>]

Ralph Hempel wrote:
> Glenn McAllister wrote:
> > We've been having some odd problems with the exponent operator ('^') and 
>
> <snip>
>
> > Host: ppc 32-bit
> >
> > Given the following script, it produces the correct results on both 
> > x86 and ppc:
> >
> >  y = 2^3
> >  print('y = ', y)
> >
> >  x = 10 % y
> >  print('x = ', x)
> >
> >  y = 2^3
> >  print('y = ', y)
> >
> > The output on both platforms is:
> >
> >  y =     8
> >  x =     2
> >  y =     8
> >
> > However, if we run the morally equivalent series of operations 
> > directly in the lua interpreter on the target ppc system, we get a 
> > different result:
> >
> >  Lua 5.1.3  Copyright (C) 1994-2008 Lua.org, PUC-Rio
> >  > x = 2^3
> >  > =x
> >  8
> >  > y = 10 % x
> >  > =y
> >  2
> >  > z = 2^3
> >  > =z
> >  4.0096609170284
>
> What happens if you run the "morally equivalent" script from a file?

Sorry, I had changed around some of the variable for the interactive 
session to show that its any assignment of 2^3 that triggers the issue, 
and not just resetting y.

If I change the script to:

 x = 2^3
 print('x = ', x)

 y = 10 % x
 print('y = ', y)

 z = 2^3
 print('z = ', z)

I get the expected output:

 x =     8
 y =     2
 z =     8

> And is the last step z = 2^3 or is it z = y^3

Its z = 2^3, which should have the value of 8.  So I'm using constants, 
not the variable.

But interestingly, if I change the last assignment in the script from

  z = 2 ^ 3

to be

 z = y ^ 3

I now get the broken output:

 x =     8
 y =     2
 z =     4.0096609170284

Adding the following to the end of the script:

 a = 2 ^ 3
 print ('a = ', a)

Gives me the following:

 x =     8
 y =     2
 z =     4.0096609170284
 a =     8

WTF?
--
Glenn McAllister     <glenn@somanetworks.com>      +1 416 348 1594
SOMA Networks, Inc.  http://www.somanetworks.com/  +1 416 977 1414