negative sqrt()

[Parham]

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"; }

and

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

and

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

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?

[Fletch]

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.

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.

[jeffa]

$ 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)