My version of the loop doesn't use goto

No, it uses redo and next, which can be worse than goto. q-: (Except perhaps from the perspective of the optimizer which doesn't bother to try to figure out goto most of the time.)

But what I'm really puzzled about is this new "naked block with lots of redo, next, and last" that I've been seeing lately. This example doesn't require anything so powerful and easy-to-abuse as that. Why not some simple loops like:

local $_;
do {
    do {
        print "> ";
        chomp( $_= <STDIN> );
    } until(  /\S/  );
} until(  'FALSE' eq cmd_select( split ' ' )  );
[download]

or

local $_;
do {
    print "> ";
    chomp( $_= <STDIN> );
} until(  /\S/  &&  'FALSE' eq cmd_select( split ' ' )  );
[download]

or even have your code handle EOF on STDIN:

local $_;
do {
    do {
        print "> ";
        defined( $_= <STDIN> )   or  die "EOF on STDIN";
        chomp( $_ );
    } until(  /\S/  );
} until(  'FALSE' eq cmd_select( split ' ' )  );
[download]

(if you need to clean up on EOF, then throw this in a sub and return instead of die)

That way your code actually looks like "loop reading commands until you get a non-empty one and loop doing that until a 'quit' is requested". Not, "here is a block that I may or may not be using as a loop (please parse the rest of the block if you want to know), read a command, goto the top of the nearest surrounding loop (or naked block but not a conditional or do block) if the command is empty, otherwise go to the continue block (if there is one) or the top of the nearest surrounding loopish block, if a 'quit' was not requested". (:

I know that something like the following is a fairly common task:

    lots of work to get next thing;
    # possibly giving up for any of several reasons
    goto TOP   if  thing isn't interesting;
    if(  thing is invalid  ) {
        instruct;
        goto TOP;
    }
    do lots of stuff with thing;
    goto TOP   if  not last thing;
    if(  no valid things found  ) {
        complain;
        return;
    }
    finish up;
    return result;
[download]

and that you can code that with a naked block and a few redos and/or nexts (which do the exact same thing in a naked block so mix them around to keep people guessing) and perhaps a last near the bottom. I mean you can do nearly anything with those almost like you can do anything with goto.

But I'd much rather stick to abusing the "early return" which I don't find hard to parse at all:

sub get_next_interesting_thing {
    do {
        return   if  ! get_next_thing;
    } until(  interesting_thing  );
    return thing;
}
sub get_next_valid_thing {
    while(  get_next_interesting_thing  ) {
        return thing   if  valid_thing;
        instruct;
    }
    return;
}

if(  ! get_next_valid_thing  ) {
    complain;
    return;
}
do {
    do lots of stuff with thing;
} while(  get_next_valid_thing  );
finish up;
return result;
[download]

(or if keeping track of having seen at least one valid thing is less work than retyping "get_next_valid_thing", then switch that bottom stuff around to look more like the original)

        - tye (but my friends call me "Tye")

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.