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Re^3: sub that sets $_

by TheDamian (Priest)
on Jun 29, 2005 at 00:04 UTC ( #470878=note: print w/replies, xml ) Need Help??

in reply to Re^2: sub that sets $_
in thread sub that sets $_

Which means that while ($z = prompt "") { will set $_ and $z. This is a bad idea. What if the code is used in an inner loop? when the outer loop uses $_ for example?
Yes, that is a nuisance. I'm working on overcoming that problem, but it's difficult: Perl never quite gives you enough context information to detect the assignment. :-(

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Re^4: sub that sets $_
by TheDamian (Priest) on Jun 29, 2005 at 00:54 UTC
    On further investigation, it appears that you can tell the two contexts apart using the Want module. Specifically, want('BOOL') knows the difference. For example:
    my $flipflop = 0; sub foo { use Want qw(want); print 'not ' if !want 'BOOL'; print "bool\n"; return $flipflop=!$flipflop; # alternate true and false } for (1..3) { while (foo() ) { # print "here 1\n"; } while ($answer = foo() ) { # print "here 2\n"; } }

    Unfortunately, under 5.8.3 I get bus errors if there I uncomment the print statements, or if there is anything in the while blocks. :-(

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[stevieb]: Thanks hippo, as do I, as if it's not, hardware peripherals or sensors could be destroyed (code has to be reliable when dealing with input/output voltages)
[hippo]: Aha - more Pi-based projects?
[stevieb]: yeah digital potentiometer

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