negative sqrt()

i ran into the problem where my program would sometimes be forced to take negative square roots. I tried to catch an error somewhere in the function, but couldn't do so. I've tried the following:

eval { $number = sqrt(-1) };
if ($@) { print "negative sqrt"; }
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and

$number = sqrt(-1) or die "error";
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and

$number = sqrt(-1) or print "error";
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all with no luck. Math::Complex manages to take negative squareroots, but i didn't wanna bother doing that. The only good solution i can come up with right now is checking for a negative number before performing the function. Any ideas on alternatives?

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(jeffa) Re: negative sqrt() by jeffa (Chancellor) on Feb 09, 2002 at 15:48 UTC
$ perldoc -f sqrt sqrt EXPR sqrt Return the square root of EXPR. If EXPR is omitted, returns square root of "$_". Only works on non-negative operands, unless you've loaded the standard Math::Complex module. use Math::Complex; print sqrt(-2); # prints 1.4142135623731i UPDATE: But i didn't really answer the question, "why can't you 'catch' this exception" ... is it possible? Why yes it is! Fletch++! jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply]
Re: negative sqrt() by Fletch (Chancellor) on Feb 09, 2002 at 16:04 UTC
The eval works fine, so long as you're not passing a constant -1 as an argument (which the compiler will catch and gripe about). Compare: `$ perl -le 'BEGIN { print "in begin" } eval { $i = <> ; $r = sqrt( -1 +) }; print ($@ ? "error: $@" : $r)' + in begin Can't take sqrt of -1 at -e line 1.` [download] with `echo -1 \| perl -le 'BEGIN { print "in begin" } eval { $i = <> ; $r = s +qrt( $i ) }; print ($@ ? "error: $@" : $r)' + in begin error: Can't take sqrt of -1 at -e line 1, <> line 1.` [download]	[reply] [d/l] [select]


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negative sqrt()

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