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From: marc@athena.mit.edu
Newsgroups: comp.lang.perl
Subject: Re: Wanna help us write The Book?
Message-ID: <1990Jul26.234220.28347@uvaarpa.Virginia.EDU>
Date: 26 Jul 90 23:42:20 GMT
Sender: mmdf@uvaarpa.Virginia.EDU (Uvaarpa Mail System)
Reply-To: marc@mit.edu
Organization: The Internet
Lines: 90

Will it be possible to see the book online before it is too late to
make changes?  I find it much easier to provide context diffs than
nebulous suggestions.

Also, here's a package I wrote which makes interactive perl scripts
easier to write.  Given an array of the form:

@menu = (
	"command1","perlsub1","help",
	"command2","perlsub2","help2",
);

It goes into a loop prompting for commands and executing them.  "exit"
exits the loop, "quit" or ^D exits the program, and "help" displays
help.

--cut--
# package, meant to be do'ed, not run directly
#
# $Id: menu.pl,v 1.1 90/07/25 02:57:15 marc Exp $
#

package menu;

@gencmds = (
	"help","__internal","Print the list of commands in this menu",
	"?","","help",
	"exit","__internal","Exit the current menu",
	"quit","__internal","Quit",
);

sub main'menu { # @_ = ($prompt,@cmds)
	local($prompt,@cmds,%fcts,%helps);

	$prompt = shift(@_);
	@table = (@_,@gencmds);

	while (@table > $[) {
		$cmd = shift(@table);
		$fct = shift(@table);
		$help = shift(@table);
		if (defined($fcts{$cmd})) {next;}
		if ($fct eq "") {
			$fct = $fcts{$help};
			$help = $helps{$help};
		}
		push(@cmds,$cmd);
		$fcts{$cmd} = $fct;
		$helps{$cmd} = $help;
	}

	while (1) {
		print "\n$prompt: ";
		if (!($_ = <>)) {
			print "eof on input.  Aborting...\n";
			exit(2);
		}
		chop;

		if (defined($fct = $fcts{$_})) {
			if ($fct eq "__internal") { # Magic...
				if (($_ eq "help") || ($_ eq "?")) {
					foreach (@cmds) {
						printf "%-15s%s\n",$_,$helps{$_};
					}
				} elsif ($_ eq "exit") {
					return;
				} elsif ($_ eq "quit") {
					exit(0);
				} else {
					die "Bogon __internal $_!\n";
				}
			} else {
				if (index($fct,"'") == ($[-1)) {
					$fct = "main'".$fct;
				}
				eval("&$fct();");
			}
		} else {
			print "\"$_\" is not a valid command.  Type ? for help.\n";
		}
	}
}
--cut--

One thing I've thought about adding is argument parsing.  Maybe even
an eval statement, so you can answer a prompt with perl code :-)
Other ideas?

		Marc