Array::Lookup

NAME

Array::Lookup - Lookup strings in arrays or hash tables with abbreviation.

SYNOPSIS

    use Array::Lookup;

    $value = lookup $key, \@keywords, \&notfound, \&toomany;

    $value = lookup $key, \%keywords, \&notfound, \&toomany;

    lookup_error $key, $keywords, $err, $msg;

DESCRIPTION

lookup

Lookup $key in the table @keywords and return the unambiguously matching keyword, if any. If the second argument is given as a hash array, %keywords, then lookup a matching key, with abbreviation, and return the value corresponding to the unambiguously matching key.

If there are no matches, invoke &notfound like this:

    &$notfound( $key, \@keywords, '');

If there are two or more matches, invoke &toomany like this:

    &$toomany( $key, \@keywords, \@matches);

If either subroutine is omitted or null, then no special action is taken except that undef is returned for the failed lookup.

Note that the third argument, the array of ambiguous matches, allows a common subroutine to be used for both error conditions and still distinguish the error.

See "lookup_error" for a standard method of handling lookup failures.

lookup_error

Handle an error for the lookup subroutine. The arguments:

$key

The search key which failed the lookup.

$keywords

The hash or array reference containing the keywords none of which matched the $key.

$err

A flag indicating if the lookup failed because of no matches at all (''), or if the lookup failed because of too many matches (\@matches);

$msg

A format string used to format and print the error message. It should contain two printf substitution sequences: %s. The first will be substituted with the failed lookup key; the second with one of the phrases: "not found" or "is ambiguous", depending upon $err.

If $msg is omitted or null, a default message will be used:

  "lookup failed: %s %s; use one of:\n"

followed by a listing of the strings in the $keywords array.

EXAMPLES

Using arrays

    use Array::Lookup;
    ...
    @keywords = qw(quit find get set show);
    ...
    $command = <STDIN>;
    $command = lookup $command, \@keywords, 
	sub { lookup_error @_, "Unknown command '%s'; use one of:\n"; },
	sub { lookup_error @_, "Command '%s' %s; use one of:\n"; };

Using hashes

    use Array::Lookup;
    ...
    %Commands = ( 'quit' => \&quit,  'get' => \&get,  'set' => \&set,
    	          'find' => \&find,  'show' => \&show );
    ...
    $input = <STDIN>;
    $command_sub = lookup $input, \%Commands, 
	sub { lookup_error @_, "Unknown command '%s'; use one of:\n"; },
	sub { lookup_error @_, "Command '%s' %s; use one of:\n"; };

AUTHOR

Alan K. Stebbens <aks@sgi.com>