hi,
im currently using this construct to read my input: 

my $formel=$ARGV[0];
my ($vorzeichen_a,$a,$vorzeichen_b,$b,$vorzeichen_c, $c) = ($formel =~
+ m/y= (\+|\-|)    #$vorzeichen_a
                                                                      
+      (.+|)   #$a
                                                                      
+      x\^2
                                                                      
+      (\+|\-|)    #$vorzeichen_b
                                                                      
+      (.+)    #$b
                                                                      
+      x
                                                                      
+      (\+|\-|)    #$vorzeichen_c
                                                                      
+      (.+)    #$c
                                                                      
+      $/x);

[download]

the input is in the form y=ax^2+bx+c, a,b or c arent needed every time.

if tried to check if they are used like this:
(a has to be 1 if unset) 

if (defined($a))
{}
else
{
   $a=1;
}

[download]

but that doesnt work, the var is always defined :(
what other options do i have?

greets
metalfan

20051224 Cleaned up by Corion: Added formatting.

In reply to if var isnt used by metalfan

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