Wc -Sx- Jones wrote:
> david wrote:
>
>> how does simply putting a piece of logic in your code and print out an
>> error meesage when a variable match a certain value prove something in
>> Perl is either true nor false? this is simply impossible in Perl because
>> you can never code a 3-way logic.
>
>
> use strict;
> use warnings;
>
> my $test = 0;
>
> ($test) ? print "\$test exists"
> : ($test > 0) ? print "\$test greater then zero"
> : ($test < 0) ? print "\$test less then zero"
> : print "\$test is zero";
>
> undef $test;
>
> (undef, $test) ? print "\$test is defined"
> : print "\$test is undefined";
>
> __END__
>
> But I was asked not to confuse...
> So ignore this posting...
>
no i am not going to ignore it :-)
tell me what exactly have you accomplished and what questions have you
answered? my statement is:
"you can never code a 3-way logic in Perl"
and then you post a bunch of code without any comment at all except telling
people to ignore your code. thus, i assume your code answer my question and
prove that you can code a 3-way logic in Perl which means:
* Perl's 'COND ? THEN : ELSE' conditional operator should never be used
because it only handles a 2-way logic: true or false
* Perl's equality and inequality operators such as ==,!=,eq,ne should never
be used because it only handles a 2-way logic: it evaluates their operants
and produce either a true or false value
* You should never uses 'if(COND)' in Perl because it only evaluates COND to
either true or false and NOT a 3-way logic as true,false or neither true
nor false
* You should never uses 'unless(COND)' in Perl for the same reason that it
only handles a 2-way logic and evaluates to either true or false and
nothing else
* You should never uses 'EXP or EXP','EXP and EXP','EXP && EXP','EXP || EXP'
in Perl because they only evaluates to true or false
* More importantly, given this simple program:
#!/usr/bin/perl -w
use strict;
my $i = $ENV{something} ? 1 : 2;
__END__
* I say $i is either 1 or 2 because $ENV{something} can only be true or
false
* You *might* be saying $i is unknown (or undef) because $ENV{something} can
be true, or false or neither true nor false which '?:' can't handle.
correct?
* finally, how useful is this:
> ($test) ? print "\$test exists"
> : ($test > 0) ? print "\$test greater then zero"
> : ($test < 0) ? print "\$test less then zero"
> : print "\$test is zero";
if $test is neither true nor false?
* do you realize "$test" is evaluated to either true or false?
* do you realize "$test > 0" is evaluated to either true or false?
* do you realize "$test < 0" is evaulated to either true or false?
david
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