Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!oliveb!bunker!garys
From: garys@bunker.UUCP (Gary M. Samuelson)
Newsgroups: comp.lang.c
Subject: Re: gotos
Message-ID: <3490@bunker.UUCP>
Date: 25 Apr 88 22:31:26 GMT
References: <1988Apr8.183815.3187@utzoo.uucp> <449@goofy.megatest.UUCP> <1988Apr11.201934.20594@utzoo.uucp> <748@l.cc.purdue.edu> <3470@bunker.UUCP> <2200@louie.udel.EDU>
Reply-To: garys@bunker.UUCP (Gary M. Samuelson)
Organization: Bunker Ramo, an Olivetti Company, Shelton, Ct
Lines: 60

In article <2200@louie.udel.EDU> new@udel.EDU (Darren New) writes:
>How about: (pseudocode)

For pseudocode it looks a lot like C.

The easy way: replace "goto handle_key" with "return."
Then after the call to this function, add a call to handle_key().
You have too much going on for it to be one function anyway.

What you really want is to get an interrupt if a key is pressed.
If you can do that, then the code becomes much simpler.  If you
can't get either a "key pressed" interrupt or an interval timer
interrupt, then use a state machine.  (Credit has to go to Dave
Burton; although I frequently use state machines, I hadn't thought of it
in the previous case.)

while( state != done ) {

/* Instead of 'state', 'next_thing_to_do' might be better */

	switch( state ) {
	case readingfile:
		...
		if( read_line[0] == special_flag_char )
			state = done;
		else
			state = inserting_spaces_and_color_codes;
		break;
	case inserting_spaces_and_color_codes:
		...
		state = displaying_text_line;
		break;
	...
	case last_thing_to_do:
		state = done;
		break;

	} /* end of switch (state) */

	if( keypressed() )
		state = done;
} /* end of while( state != done ) */

c = wait_for_key_then_read_it();
switch (c) {
      case 'A': ...
       ...
}

It still reads sequentially, but now "if keypressed" is isolated,
which makes it less cluttered, and easier to change if (no, when)
it becomes necessary to do any of the following:
	1. pass an argument to keypressed();
	2. check something else periodically;
	3. add or delete points at which the check is made;

>I would like to see a goto-less version of this that is easier to understand.

I hope you think I have done so.

Gary Samuelson