A more specific and illustrative example is $small+$huge1-$huge2 where ($small+$huge1)-$huge2 is easily much less accurate than $small+($huge1-$huge2) (where parens imply order of evaluation, which isn't always the case).

For example: 

#!/usr/bin/perl -lw
use strict;
my $h1= my $h2= 1e20;
my $s= 1.2345;
print $s+$h1-$h2;
print $s+($h1-$h2);
__END__
0
1.2345

[download]

(I'd actually be surprised to see an example where the difference you proposed, ($a+$b+$c)/$d vs $a/$d+$b/$d+$c/$d, made more than a couple of least-significant bits of difference in the result -- though that would be enough to thwart the use of ==, of course.)

- tye        

In reply to Re^4: Why does perl math suck? (order) by tye
in thread Why does perl math suck? by sharkey

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