OpenEuphoria

2. Re: with entry and goto statement

• Posted by petelomax Dec 31, 2010
• 1730 views

There shouldn't be an example. As a beginner, you should consider the goto statement as pure evil, something you use once-in-a-decade, when you really have no other choice. If you have a block of code that you need to invoke from several places, put it in a subroutine.

Regards, Pete

4. Re: with entry and goto statement

• Posted by jeremy (admin) Dec 31, 2010
• 1703 views

I'm with you 100%. GOTO is a very valid and powerful tool that should be used much more than it currently is. It can greatly simplify code make it more clean, easier to maintain and easier to understand. However, as programmers in todays age we have been "programmed" to think it's a terrible evil. This is not true.

When reading the history of GOTO, the first paper published against it was when languages used almost ALL goto's for EVERY loop construct. No way I would program like that today. We have, now, nice loops such as for, while and loop. We have if blocks instead of a single if X goto Y statment, etc... GOTO certainly should not be used for every jump that exists but goto is far from evil. It's beautiful!

What I see as worse than goto is returning from a function in 5 different places on error conditions or deeply nesting if statments checking for these error conditions so you can have only one exit point and not have to use goto. This is evil. Goto can be used and should be used in such situations. Code will, again, be much more readable, concise, understandable and maintainable.

People should not be afraid of goto. People should not replace if, while, loop, for with a goto. People should not have a hundred exit points from their functions. People should not break their functions into illogical blocks to avoid a goto. The Euphoria standard library uses goto in a few well placed situations. All of your translated applications use goto. There are many valid uses. I just posted a message about Best Practices, I think some valid examples of goto should be placed there to help everyone decide when to and when not to use goto. But to say it's evil is incorrect in my book. Now, global? That's another story global is evil (in most situations ) but even it has a place ;-D

Jeremy

6. Re: with entry and goto statement

• Posted by jeremy (admin) Dec 31, 2010
• 1628 views

I just stumbled across this thread from Linus Torvalds:

From: Linus Torvalds 
Subject: Re: any chance of 2.6.0-test*? 
Date: 	Sun, 12 Jan 2003 12:22:26 -0800 (PST) 
On Sun, 12 Jan 2003, Rob Wilkens wrote: 
> 
> However, I have always been taught, and have always believed that 
> "goto"s are inherently evil.  They are the creators of spaghetti code 
 
No, you've been brainwashed by CS people who thought that Niklaus Wirth 
actually knew what he was talking about. He didn't. He doesn't have a 
frigging clue. 
 
> (you start reading through the code to understand it (months or years 
> after its written), and suddenly you jump to somewhere totally 
> unrelated, and then jump somewhere else backwards, and it all gets ugly 
> quickly).  This makes later debugging of code total hell. 
 
Any if-statement is a goto. As are all structured loops. 
And sometimes structure is good. When it's good, you should use it. 
And sometimes structure is _bad_, and gets into the way, and using a 
"goto" is just much clearer. 
 
For example, it is quite common to have conditionals THAT DO NOT NEST. 
In which case you have two possibilities 
- use goto, and be happy, since it doesn't enforce nesting 
This makes the code _more_ readable, since the code just does what 
the algorithm says it should do. 
- duplicate the code, and rewrite it in a nesting form so that you can 
use the structured jumps. 
This often makes the code much LESS readable, harder to maintain, 
and bigger. 
 
The Pascal language is a prime example of the latter problem. Because it 
doesn't have a "break" statement, loops in (traditional) Pascal end up 
often looking like total shit, because you have to add totally arbitrary 
logic to say "I'm done now". 
 
Linus 

8. Re: with entry and goto statement

• Posted by jeremy (admin) Dec 31, 2010
• 1619 views

Euphoria is amongst the best (dare I say) with this. I think by break, you mean exit. exit alone always exits from the containing loop. You can, however, have labels:

while 1 label "for-ever" do 
    for i = 1 to length(families) label "each-family" do 
        sequence children = families[i][CHILDREN] 
        for j = 1 to length(children) label "each-child" do 
            if equal(children[j][NAME], "John Doe") then 
                exit -- exits the containing loop, 'each-child' 
            elsif equal(children[j][NAME], "Jane Doe") then 
                exit "each-family" -- exits from the 'each-family' loop 
            elsif equal(children[j][NAME], "Jeff Doe") then 
                exit "for-ever" -- exit all three loops 
            end if 
        end for 
    end for 
end while 

Now, as you say, poorly written, break, exit, continue and retry can all make some terrible code. They are powerful when used correctly and a virtual disaster when poorly written.

Jeremy

10. Re: with entry and goto statement

• Posted by jaygade Dec 31, 2010
• 1658 views

Because we aren't programming in machine language or assembler. We're programming at a higher level with better abstractions, abstractions which should hopefully be clearer.

Which is the abstraction. You know exactly where the program will branch and you do not end up with spaghetti code.

Back when I first started programming in BASIC, GOTO and GOSUB were all there was. There wasn't even an "ELSE" clause. And we had to use line numbers instead of labels, which are themselves an abstraction.

Okay. And? That's like apples and oranges. Or apples and bowling balls, rather.

12. Re: with entry and goto statement

• Posted by jeremy (admin) Jan 01, 2011
• 1564 views

Indeed, but not to the point of those who came before us and made a whole crop of programmers who are so afraid of goto they cease to use a language or a library that has or uses a goto statement. goto is a very valid, powerful and elegant solution in quite a few cases once you understand its proper use.

Jeremy

14. Re: with entry and goto statement

• Posted by jaygade Jan 01, 2011
• 1569 views

Users are not the same as programmers. Programs perform a specific task. Users are much more freeform in their actions.

I just don't see the comparison.

16. Re: with entry and goto statement

• Posted by Vinoba Jan 01, 2011
• 1503 views

Contradictions in your statements abound. If one accepts that programmers have MORE knowledge of the tools they are using than End Users, and then accept your argument that users need a lot of freedom in their actions, which we often successfully endeavor to give then it is fair conclusion to accept that we, the programmers, have even better ability to do our "GOTOs" than the end user has.

How can we, the application programmers, give a thousand GOTOs to our end users in a program WHICH THEY DID NOT CREATE THEMSELVES, when we ourselves don't have the ability to navigate though a program of our own creation? If they have the ability to navigate through an unknown program, we, with better abilities than them, should have the ability to navigate though a program of our own creation.

Anyway, this discussion is not leading us anywhere. So Happy New year to you and your family. Happy programming with version 4.0.

18. Re: with entry and goto statement

• Posted by jaygade Jan 01, 2011
• 1429 views

Because we do not. Every action by the user, either at the command line or even at the gui, is more akin to a function or procedure call than to a lowly goto. It is only a goto at the lowest, least abstract level.

20. Re: with entry and goto statement

• Posted by bill Jan 08, 2011
• 1344 views

name them

That is Jeremy, specify the places in a program where goto is necessary. I think it is where you need a bail out clause. Is this what you are referring to? Or do you have a another use?