Contextual::Return Contextual::Return is a Perl module to create context-senstive return values.
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Perl module return context-senstive values return values context-senstive

Contextual::Return Description

Contextual::Return is a Perl module to create context-senstive return values. Contextual::Return is a Perl module to create context-senstive return values.SYNOPSIS use Contextual::Return; use Carp; sub foo { return SCALAR { 'thirty-twelve' } BOOL { 1 } NUM { 7*6 } STR { 'forty-two' } LIST { 1,2,3 } HASHREF { {name => 'foo', value => 99} } ARRAYREF { } GLOBREF { *STDOUT } CODEREF { croak "Don't use this result as code!"; } ; } # and later... if (my $foo = foo()) { for my $count (1..$foo) { print "$count: $foo is:n" . " array: @{$foo}n" . " hash: $foo->{name} => $foo->{value}n" ; } print {$foo} $foo->(); }Usually, when you need to create a subroutine that returns different values in different contexts (list, scalar, or void), you write something like: sub get_server_status { my ($server_ID) = @_; # Acquire server data somehow... my %server_data = _ascertain_server_status($server_ID); # Return different components of that data, # depending on call context... if (wantarray()) { return @server_data{ qw(name uptime load users) }; } if (defined wantarray()) { return $server_data{load}; } if (!defined wantarray()) { carp 'Useless use of get_server_status() in void context'; return; } else { croak q{Bad context! No biscuit!}; } }That works okay, but the code could certainly be more readable. In its simplest usage, this module makes that code more readable by providing three subroutines--LIST(), SCALAR(), VOID()--that are true only when the current subroutine is called in the corresponding context: use Contextual::Return; sub get_server_status { my ($server_ID) = @_; # Acquire server data somehow... my %server_data = _ascertain_server_status($server_ID); # Return different components of that data # depending on call context... if (LIST) { return @server_data{ qw(name uptime load users) } } if (SCALAR) { return $server_data{load} } if (VOID) { print "$server_data{load}n" } else { croak q{Bad context! No biscuit!} } }Contextual returnsThose three subroutines can also be used in another way: as labels on a series of contextual return blocks (collectively known as a context sequence). When a context sequence is returned, it automatically selects the appropriate contextual return block for the calling context. So the previous example could be written even more cleanly as: use Contextual::Return; sub get_server_status { my ($server_ID) = @_; # Acquire server data somehow... my %server_data = _ascertain_server_status($server_ID); # Return different components of that data # depending on call context... return ( LIST { return @server_data{ qw(name uptime load users) } } SCALAR { return $server_data{load} } VOID { print "$server_data{load}n" } DEFAULT { croak q{Bad context! No biscuit!} } ); }The context sequence automatically selects the appropriate block for each call context. Requirements: · Perl · version.pm · Want.pm

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