I'm building a diagnostic medical questionnaire using Perl Tk. Need to
create a Tk callback process for several hundred sub routines.
I've experimented with the following code. It does recognize the two
subroutines "foo" and "moo", but calls only the first
subroutine "foo"; it does give correct answer. It doesn't call "moo." Perl
Cookbook indicates use of backslash operator
to create a reference to a named function but not for unnamed ones. Can
anyone show me what I'm doing wrong?
Thanks
John Burns
#!/usr/local/bin/perl
use warnings;
# reference_to_functions8.pl
# Dispatch Tables
# See Making Sense of Subroutines
#by Rob Kinyon | Pages: 1, 2, 3, 4
# Adding and removing available subroutines is
# simpler than the if-elsif-else scenario, and
# this is much safer than the soft references scenario.
# Perl Cookbook 11.4 shows following example
my %dispatch = (
"foo" => sub {
my $x = 3;
my $ans = ($x**2);
print "answer is: $ans \n"; #prints "answer is: 9"
},
"moo" => sub {
my @data = (3,5,13);
my $radius;
my $radius_ref = @data;
foreach $radius(@$radius_ref) {
print "my radius is: $radius \n";
my $area = 3.14159 * ( $radius ** 2);
print "and circle area is $area \n";
}
}
);
my $name;
my $key;
my $dispatch;
#use following to test for key name in hash
foreach $name("foo", "moo") {
if (exists $dispatch{$name}) {
print "$name is a subroutine.\n";
}
else {
print "$name is not a subroutine.\n";
}
}
#use following to test for presence of a key in a hash
foreach $key (keys %dispatch) {
print "$key => $dispatch->{$key}\n"
}
my $input;
foreach $input("foo", "moo"){ #PCB 11.4 uses chomp($input = <STDIN>) in
lieu of "foreach"
if ( exists $dispatch{ $input } ) {
$dispatch{ $input }->( );
}
else {
die "Cannot find the subroutine $input\n";
}
}
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