Re^2: Determining whether a value is zero.

It works only if I do not touch (i.e. expose it to various contexts) the variable before running the test:

for my $x (0,
           "0",
           0.0,
           dualvar(0,1),
           dualvar(0,"0 "),
            '----------------',
            1,
            "foo",
            "00",
           "0 ",
           undef,
           "",
           dualvar(1,0),
           "0.0",
          ) {
    print "$x before: ",is_zero($x),"\n";
    my $y = ($x+1.1).$x;
    print "$x after:  ",is_zero($x),"\n";
}
[download]

Comment on Re^2: Determining whether a value is zero. Download Code

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Re^3: Determining whether a value is zero. by ikegami (Patriarch) on Mar 11, 2011 at 08:56 UTC
It works as per the OP's spec. Don't blame me for his spec being awful! For strings, `0+$x; #Upd: Or 1.1 or whatever` [download] is effectively `$x = dualvar(0+$x, $x) if looks_like_number($x);` [download] The OP was clear that `dualvar(0, $anything)` should be considered zero.	[reply] [d/l] [select]
Re^4: Determining whether a value is zero. by choroba (Cardinal) on Mar 11, 2011 at 09:34 UTC
~~dualvar 0,~~"0 " is considered zero after the assignment to $y in my code. That is against the specification I fear... UPDATE: corrected.	[reply]
Re^5: Determining whether a value is zero. by JavaFan (Canon) on Mar 11, 2011 at 10:21 UTC
No. In fact, after your initial reply, I particular pointed out that your first code incorrectly considers `dualvar 0, "0 "` to be not be a zero. `dualvar 0, ANYTHING` should be considered a zero.	[reply] [d/l] [select]
Re^6: Determining whether a value is zero. by choroba (Cardinal) on Mar 11, 2011 at 10:40 UTC
Re^5: Determining whether a value is zero. by ikegami (Patriarch) on Mar 11, 2011 at 18:11 UTC
"0 " is considered zero after the assignment to $y in my code You never test `"0 "` after the assignment to $y. You test `dualvar(0, "0 ")`. Please re-read my post.	[reply] [d/l] [select]
Re^6: Determining whether a value is zero. by choroba (Cardinal) on Mar 11, 2011 at 22:32 UTC
Re^3: Determining whether a value is zero. by JavaFan (Canon) on Mar 11, 2011 at 11:08 UTC
It works only if I do not touch (i.e. expose it to various contexts) the variable before running the test: Well, yes. That's because looking at variables in Perl can actually modify them.	[reply]