Evils of GOSUB?

[BruceG]

I have seen in many programming books that it is generally bad practice to use GOTOs and GOSUBs. The GOTO issue I can appreciate; no self-respecting programmer wants to write spaghetti code. However, I don't see anything wrong with occasionally using GOSUBs to repeat a section of code within a Sub or Function. Does anyone have a convincing argument as to why GOSUB should be avoided?

[Mark Sreeves]

I've never used GoSub in VB and I had to look in the help file to see what it does!


the help file says:

Creating separate procedures that you can call may provide a more structured alternative to using GoSub...Return.



I first started programming with Modula2 which doesn't even have GOTO or GOSUB in the language so it forces you into writing well structured programs.

So, to anwer you question; no I can't offer a convincing argument against GoSubs. Has Gosub been left in VB to make it backward-compatable with older versions of Basic?

[Sam Finch]

There's a lot of stuff left in VB to make it backwards compatible, Gosub's probably usefull in very rare occasions, If you have a procedure with lots of private variables and a subroutine that you only called from that procedure which changed a lot of variables then it's probably excusable to use a gosub for speed purposes rather than having to pass all the variables around. but there's probably a better way round it. (a largs UDT passed by ref for example.

[kedaman]

Gosub's are faster than Subs and functions so when at procedurelevel called repeated code is used and no loops matches, Gosub can be useful. I'm not saying im using it frequently, as you need very frequently used code to notice any better performance.

[BruceG]

Thanks for the input, guys. I agree with Sam and Kedaman, and I do only use it in the limited situations described. Although GOSUB is probably included in VB for backwards compatibility, I still find it useful in these situations. Back in the days of QBasic, using GOSUBs was the primary way to write structured code. Not to show my age or anything, but GOSUB is similar to using PERFORM in COBOL (cringe), where PERFORM is the way to structure those beastly COBOL programs. Anyway, you guys confirmed my line of thinking. Thanks again.

[Juan Carlos Rey]

However all that scrap against GOTO, it is one of the fastest functions in VB, and in many other languages too, as it is implemented directly in machine code.

It is also the best way to unstructure the code, thou.

There is a situation in which goto is the best choice: trying to get out of a deeply nested for-next or do-loop routine when a condition comes true. Instead of multiple exit for (or exit do)- one single GOTO will take you out fast and neatly.

[kedaman]

That's correct, i've used goto several times in such cases and it's definitely the fastest way to jump somewhere, so don't do any crappy do:for:if:while: and then have it all exit for, do until while or exit in other ways than goto, which is the clean way to do it. Also how do you exit an if?

Whodo you exit an if? you mean IF as in the If...Then... statement? Just use End If

Tend not to use gosub and goto in vb, except for On Error conditions....apparent improved in vb7. However we have a couple of bank clients...and in there software GOTOs are used for speed. Yes bad coding technique in theory, in reality needed to cope with the amount of through put. Generally they pay big bucks if we can speed up an app...therefore GOTOs....but we have strict coding standards to keep control of the things.

Once had to support a COBOL app which was all GOTOs not one PERFORM statement...man could take days to fix even simple bugs.

[Juan Carlos Rey]

You mean that Completely Obsolete Business Oriented Language?

Do not abuse GOTO's -keep jumps short too.

[BruceG]

Good one, Juan. Thanks for your earlier advice. Thanks also to Jethro and Megatron for your input. Now if only my posts regarding the TreeView control generated as many responses ...

[kedaman]

Meg, no End if is the end of an if, like end sub is the end of a sub. Why isn't there any exit ifs?

IF condition then
 .
 .
 50 lines of code
 .
 exit if
 . 
 100 lines of code
 .
 .
end if

Except when you have a goto

[Paul282]

I didn't realize that GoSub was still in the language !!!
I remember it from QB & TRS80 days

don't really nead it, haven't really thought about it

GoSub and Wend and probably a bunch of others are really old, but are still part of the original BASIC language, so MS probablky wanted to keep them.

P.S, what is TRS80???

[Paul282]

Once apon a time (about 15+ years ago) there was a computer by radioshack called a TRS-80, you pluged it into the TV and it's OS was a flashing cursor that you could type basic into and save it to cassette! There were a few types, mine had 16kilobytes of ram, no HDD etc. the "BIG" ones had 512k ram and more colours (same os though)

It was around between the time of the Commodor Vic-20 and C-64.

I don't suppose you remember the ads?

"Are you keeping up with the Commodor?, 'cause the commodor's keeping up with you!"

But it didn't keep up because I don't think they made any after the C-64 which was quite popular for games before the Atari-ST and Amiga hit the market

bit of history there for the school kids!

[kedaman]

Also another good thing with goto:

 Do
  lines
  goto label
  lines
 loop
 lines
label:
 lines

Paul282: I probably wasen't even born back then...Did they actually have any good programs for the computers?

[Fox]

Kedaman, you won't ever need that. You have to check something to know if you need to exit the if. And when you're checking that you can put the rest of the code in this if statement. See:

IF condition then
  .
  .
  50 lines of code
  .
  If condition Then
     'exit if

  Else
     100 lines of code
  End If
  .
  .
End If

[Al Smith]

Hi,
affectionately known as the trash 80.
Al.

[Paul282]

Well,

I thought so at the time :-)

I was about 13, and comuters weren't that common in the home and more often than not just for games anyway, didn't even know anyone with a modem back then. Decent games didn't really appear till the C-64, then the Atari-ST and Amiga started to bring some better graphics in (8-bit)

text based games were bigger back then because of the poor graphics too.

Although a friend of mine had an apple-IIe (green screen) and people marvelled at the 128k of ram, that had some good games. Rescue raiders, Chop-lifter, taipan, Karateka. Also had a printer and 5 1/4 inch drive which was pretty impressive.


I'm starting to feel old...

[Paul282]

Originally posted by Al Smith
Hi,
affectionately known as the trash 80.
Al.

hahah, you know it then!

Has anyone heard of TI83's? We're going to have to use them next week in my course, and i have no clue what they are.

[kedaman]

Actually fox, i have more complicated structures than that, i have one starting from do with 80 lines and indeting level to 14, and i have no goto's there, not one, but it surely is confusing to run trough it. And for my latest and in my opinion best application, is using goto in a select case based structure (to exit the select case) Can you that in another way too Fox?

Also, Meg, TI83 is my best friend, it's a graphical calculator with inbuilt programming language and can be connected to your pc, and it handles complex values and everything, TI83 is great!

[Paul282]

indents to 14 levels ????

couln't you have thrown a function or two in there somewhere?

seems a bit excessive.

[Fox]

Since there is no break() or continue() in VB I dont think so Maybe you should put the code in functions to make it easier to handle... I never use GoTos in my code

[kedaman]

Hehe, of course i have functions, but that in project i made alot of my functions inline

Jump, goto, jump fast, jump with goto all time, hey exit select and exit if would be nice in vb7...