[BUG] Gosub throws a error on exit

Author

Message

Green7

18

Years of Service

User Offline

Joined: 23rd Nov 2005

Location: Switzerland

Posted: 16th Sep 2017 12:41

Link

this code throws "Encountered a RETURN statement when not in a GOSUB in at line 0" at me when i exit by "esc" key. guess gosubs are not that fancy...?

+ Code Snippet

// Project: test 
// Created: 2017-09-16

SetWindowSize( 1024, 768, 0 )

do
    gosub test
    
    if GetRawKeyPressed(27) then exit
    
    Sync()
loop
    
    
    test:
    
		Print( ScreenFPS() )
    
    return

Back to top

Profile PM Website

Markus

Valued Member

20

Years of Service

User Offline

Joined: 10th Apr 2004

Location: Germany

Posted: 16th Sep 2017 13:10 Edited at: 16th Sep 2017 13:11

Link

not a bug

you forgot the end after the loop, so it run in the test: without a gosub call , thats why return is confused

loop
end

AGK (Steam) V2017.08.16 : Windows 10 Pro 64 Bit : AMD (17.7.2) Radeon R7 265 : Mac mini OS Sierra (10.12.2)

Back to top

Profile PM Email

Mobiius

Valued Member

21

Years of Service

User Offline

Joined: 27th Feb 2003

Location: The Cold North

Posted: 18th Sep 2017 09:13

Link

GoSubs are evil. (Personal opinion.)

Click here for VR Legend of Zelda stuff

Back to top

Profile PM Email Website

Kevin Picone

21

Years of Service

User Offline

Joined: 27th Aug 2002

Location: Australia

Posted: 18th Sep 2017 14:16

Link

so use more of them ?

PlayBASIC To HTML5/WEB - Convert PlayBASIC To Machine Code

Back to top

Profile PM Website

CJB

Valued Member

20

Years of Service

User Offline

Joined: 10th Feb 2004

Location: Essex, UK

Posted: 18th Sep 2017 17:19 Edited at: 18th Sep 2017 17:20

Link

Your code exits the do-loop when the user hits esc, so the execution continues after the LOOP... eventually hitting the spurious RETURN after displaying the frame rate one last time. If you want to get all retro with GOSUB, then why not throw in a GOTO as well! Replace "then exit" with "then goto finish", and add another label at the bottom of your code:

+ Code Snippet

// Project: test 
// Created: 2017-09-16
 
SetWindowSize( 1024, 768, 0 )
 
do
    gosub test
     
    if GetRawKeyPressed(27) then goto finish
     
    Sync()
loop
     
     
    test:
     
        Print( ScreenFPS() )
     
    return

finish:

Aaargh! Ducks!
Phone Tap!
Uzmadesign

Back to top

Profile PM Email Website

BatVink

Moderator

21

Years of Service

User Offline

Joined: 4th Apr 2003

Location: Gods own County, UK

Posted: 18th Sep 2017 17:31

Link

This is a code diagram of what CJB said:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Quidquid latine dictum sit, altum sonatur
TutCity is being rebuilt

Back to top

Profile PM Email

Markus

Valued Member

20

Years of Service

User Offline

Joined: 10th Apr 2004

Location: Germany

Posted: 18th Sep 2017 18:07

Link

Quote: "
SetWindowSize(1024, 768, 0)
repeat
Print(ScreenFPS())
Sync()
until GetRawKeyPressed(27)
"

before code diagram

AGK (Steam) V2017.08.16 : Windows 10 Pro 64 Bit : AMD (17.7.2) Radeon R7 265 : Mac mini OS Sierra (10.12.2)

Attachments

Login to view attachments

Back to top

Profile PM Email

ShaunRW

DBPro Developer

16

Years of Service

User Offline

Joined: 7th Jan 2008

Location: Brisbane, Australia

Posted: 19th Sep 2017 03:15

Link

I haven't used gotos or gosubs since my learning darkbasic days, but I don't think gosubs are really that bad. IMO theres not much difference visually between CjBs code and this.

+ Code Snippet

// Project: test 
// Created: 2017-09-16
  
SetWindowSize( 1024, 768, 0 )
  
do
    test()
      
    if GetRawKeyPressed(27) then finish()
      
    Sync()
loop
      
      
function test()
    Print( ScreenFPS() )
endfunction
 
function finish()
	end
endfunction

Goto's on the other hand, should be avoided like the plague, as that does lead to creating unmaintainable mess.

Back to top

Profile PM Email

Markus

Valued Member

20

Years of Service

User Offline

Joined: 10th Apr 2004

Location: Germany

Posted: 19th Sep 2017 07:35

Link

OT

Quote: "lead to creating unmaintainable mess."

agree, its better to encapsulate a task, you see what go in and come out.

pro function
encapsulate
can used recursive
versus
speed / overhead in design

pro gosub
speed
versus
encapsulate

AGK (Steam) V2017.08.16 : Windows 10 Pro 64 Bit : AMD (17.7.2) Radeon R7 265 : Mac mini OS Sierra (10.12.2)

Back to top

Profile PM Email

Scraggle

Moderator

20

Years of Service

User Offline

Joined: 10th Jul 2003

Location: Yorkshire

Posted: 19th Sep 2017 08:16 Edited at: 19th Sep 2017 08:17

Link

Oh no!!

The Goto/Gosub debate has reared it's ugly head again!

Personally, I don't use them but to play Devil's advocate, here's a time when using Goto actually makes sense:

+ Code Snippet

do
	//do stuff
	if GetRawKeyPressed(27) then goto endProgram
	sync()
loop

endProgram:
	DeleteAllImages()
	DeleteAllObjects()
	DeleteAllSprites()
	DeleteAllText()
	end

Although, to be fair, I believe that AppGameKit handles all of that internally anyway.

The original question has been answered - the code drops out of the loop and then hits a Return without jumping there from a Gosub - hence the error.
Can we now all agree that Goto and Gosub have their uses but most seasoned coders tend to avoid them?

Happy Flapper
Additional Image Functions (9 sprite slicing etc.)
Additional String Functions
XML read, write, parse
Black theme for Geeny
RGB->HSV->RGB

Back to top

Profile PM Email

Green7

18

Years of Service

User Offline

Joined: 23rd Nov 2005

Location: Switzerland

Posted: 19th Sep 2017 08:27

Link

thanks for all the suggestions... i have now chosen to use a function instead.

Back to top

Profile PM Website

BatVink

Moderator

21

Years of Service

User Offline

Joined: 4th Apr 2003

Location: Gods own County, UK

Posted: 19th Sep 2017 08:42 Edited at: 19th Sep 2017 08:43

Link

The only language I have needed to use goto in, is VBA (Visual Basic for Applications). This language is missing exit commands from loops.

This code:

+ Code Snippet

do
    //do stuff
    if GetRawKeyPressed(27) then goto endProgram
    sync()
loop

can be written as:

+ Code Snippet

do
    //do stuff
    if GetRawKeyPressed(27) then exit
    sync()
loop

I don't know the full technical details, but exit will do a tidier job than goto, which will leave rubbish on the stack.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Quidquid latine dictum sit, altum sonatur
TutCity is being rebuilt

Back to top

Profile PM Email

Supertino

6

Years of Service

User Offline

Joined: 22nd Jun 2017

Location: Behind you!

Posted: 19th Sep 2017 09:13

Link

GoTo's have a place I think , I've used them to quickly escape a 'multi-level' for\next loop within a do\loop just slap the goto label after the loop and I can get out of the whole thing with a single call. That's the only scenario use them in though for readability Functions are superior.

Checkout my PC/MAC games on itch.io | Checkout my STEAM games | Checkout my ANDROID games

Back to top

Profile PM Website

CJB

Valued Member

20

Years of Service

User Offline

Joined: 10th Feb 2004

Location: Essex, UK

Posted: 19th Sep 2017 10:05

Link

Meh.

Gosub and Goto = Old
Functions = New

Both can = spaghetti if in the wrong hands.

Aaargh! Ducks!
Phone Tap!
Uzmadesign

Back to top

Profile PM Email Website

Mobiius

Valued Member

21

Years of Service

User Offline

Joined: 27th Feb 2003

Location: The Cold North

Posted: 19th Sep 2017 10:09

Link

Quote: "GoTo's have a place I think ,"

No.

Click here for VR Legend of Zelda stuff

Back to top

Profile PM Email Website

CJB

Valued Member

20

Years of Service

User Offline

Joined: 10th Feb 2004

Location: Essex, UK

Posted: 19th Sep 2017 10:21

Link

Quote: "No."

Lol.... you can exit a for loop in VBA using "exit for".

Aaargh! Ducks!
Phone Tap!
Uzmadesign

Back to top

Profile PM Email Website

BatVink

Moderator

21

Years of Service

User Offline

Joined: 4th Apr 2003

Location: Gods own County, UK

Posted: 19th Sep 2017 12:57

Link

Quote: "you can exit a for loop in VBA using "exit for""

You can't continue a For loop either (i.e jump to the next iteration).

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Quidquid latine dictum sit, altum sonatur
TutCity is being rebuilt

Back to top

Profile PM Email

Kevin Cross

20

Years of Service

User Offline

Joined: 15th Nov 2003

Location: London, UK

Posted: 26th Sep 2017 13:40 Edited at: 26th Sep 2017 13:44

Link

@CJB you can't exit all loops when nested using exit on it's own. It just exits the loop it's added to i.e. the below code will still loop through x 2 to 5.

+ Code Snippet

for x = 1 to 5
	for y = 1 to 5
		if (y = 2) then exit
		print(str(x) + "," + str(y))
	next
next

This will print

1,1
2,1
3,1
4,1
5,1

There might be times when you want to jump out of both loops which is when a goto works

+ Code Snippet

for x = 1 to 5
	for y = 1 to 5
		if (y = 2) then goto exitLoop
		print(str(x) + "," + str(y))
	next
next
exitLoop:

This will print

1,1

One example would be searching a grid for an item/object/value and exiting when you've found the x and y position in that grid without checking the rest of the grid.

Back to top

Profile PM Email

ShaunRW

DBPro Developer

16

Years of Service

User Offline

Joined: 7th Jan 2008

Location: Brisbane, Australia

Posted: 26th Sep 2017 13:55

Link

@Kevin Cross: When I need to exit nested loops I just manually finish the for loop by setting the iterated variable to its max value.

+ Code Snippet

for x = 1 to 5
	for y = 1 to 5
		if (y = 2)
			x=5 // exits out of for x loop
			exit // exits out of for y loop
		endif
		print(str(x) + "," + str(y))
	next
next

Back to top

Profile PM Email

Kevin Cross

20

Years of Service

User Offline

Joined: 15th Nov 2003

Location: London, UK

Posted: 26th Sep 2017 14:00

Link

@ShaunRW thanks for the tip.

Back to top

Profile PM Email

tmu

7

Years of Service

User Offline

Joined: 2nd Feb 2017

Location:

Posted: 26th Sep 2017 17:33

Link

Goto the corner. You have been very naughty.

Back to top

Profile PM

Dybing

12

Years of Service

User Offline

Joined: 12th Sep 2011

Location: Bergen, Norway

Posted: 26th Sep 2017 22:35

Link

By @BatVink:

Quote: "The only language I have needed to use goto in, is VBA (Visual Basic for Applications). This language is missing exit commands from loops.

This code:

+ Code Snippet

do
    //do stuff
    if GetRawKeyPressed(27) then goto endProgram
    sync()
loop

can be written as:

+ Code Snippet

do
    //do stuff
    if GetRawKeyPressed(27) then exit
    sync()
loop

I don't know the full technical details, but exit will do a tidier job than goto, which will leave rubbish on the stack."

Whilst certainly an improvement, arbitrary exit points is nearly as bad as arbitrary entry points (which is the real reason GOTO is pure distilled evil, as it combines both traits).

What I'd do is simpler and safer:

+ Code Snippet

repeat
    //do stuff
    sync()
until GetRawKeyPressed(27)

Allthough to be honest, in a real world application, I'd extract all the input logic to some function, and set a flag that gets checked the status of at the end.

And since we've established a long time ago that GOTO is evil, it's little brother the GOSUB is at least deviously mischievous

Functions rules - at least in AppGameKit which doesn't have a trace of OO in tier 1. Not that that is a bad thing as such, but there is a tool in my box of tricks missing...

Back to top

Profile PM

Sorry your browser is not supported!

AppGameKit Classic Chat / [BUG] Gosub throws a error on exit

Attachments