SPUG: Behavior of &&'ed functions

[John W. Krahn]

John Costello wrote:
> I have some code which boils down to the example shown below.  I expected 
> to see four lines of output, with $column incremented twice.  Instead, the 
> first print statement in each block does not output.  Instead, the second 
> and third lines are performed and apparently the first print outputs the 
> boolean evaluation of &&'ed statements.  Why does Perl (5.8.0) behave this 
> way?
> 
> Enlightenment appreciated.
> 
> 
> #!/localdepot/perl-5.80/bin/perl -w
> # test6.pl
> use strict;
> 
> my ($column);
> 
> $column = 0;
> 
> print "column is: $column\n"
> && ++$column
> && print "now column is: $column\n";
> 
> print "and column is: $column\n"
> && $column++
> && print "and now column is: $column\n";
> 
> 
>>./test6.pl
> 
> now column is: 1
> 1and now column is: 2
> 1

To see what is happening use the B::Deparse module.

$ perl -MO=Deparse,-p -e'print "column is: $column\n" && ++$column && print 
"now column is: $column\n";'
print((("column is: $column\n" && (++$column)) && print("now column is: 
$column\n")));
-e syntax OK



John
-- 
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program
fulfillment