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How to use DEF to make your own commands

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TheV360Created:
Learning how to use DEF will help you write better programs, and also be able to use libraries and other cool features of SmileBASIC. It will also help you if you plan on working with other programming languages.

DEF vs. GOSUB

If you have used GOSUB before, DEF isn't really that different. The only major difference is:
  • GOSUB is not used in programming languages anymore
  • DEF is used in almost all programming languages
Like GOSUB, DEF lets you make a bunch of code and repeat it when you need it. Unlike GOSUB, DEF has full support for parameters, which are variables that are set at the beginning of a DEF. DEF makes better looking code compared to GOSUB, and DEF also makes code more readable.
SPEAK "Hello, world!"
DEF SPEAK S$
 FOR I=0 TO LEN(S$)-1
  VSYNC 5
  ?S$[I];
  BEEP
 NEXT
 VSYNC 60
END

'vs GOSUB:

S$="Hello, world!"
GOSUB @SPEAK
@SPEAK
 FOR I=0 TO LEN(S$)-1
  VSYNC 5
  ?S$[I];
  BEEP
 NEXT
 VSYNC 60
RETURN
Also, if the next line of code is a DEF, it automatically starts ignoring what code is inside the DEF, unlike GOSUB, which would run through the code until it hits a RETURN and gives an error.

How to use DEF

There are 3 different DEF types:
  • DEF name(v1,v2,...)
    • Takes: up to 255 values, or even 0 values.
    • Gives back: 1 value.
  • DEF name v1,v2,...
    • Takes: up to 255 values, or even 0 values.
    • Gives back: nothing.
  • DEF name v1,v2,... OUT o1,o2
    • Takes: up to 255 values, or even 0 values.
    • Gives back: up to 255 values.
Each DEF is ended with an END statement. For example:
DEF HELLOWORLD S$
 PRINT S$
 BEEP
 WAIT 30
 PRINT "Hello World!"
END
will be finished soon...
ResourcesBasic Tutorials
brennfett#1
Anything a gosub can do that a DEF can't? Only thing i know is gosub/goto
Yolkai#2
Replying to:brennfett
Anything a gosub can do that a DEF can't? Only thing i know is gosub/goto
Avoid a new scope, I guess? (which is usually, if not always, a bad/inconvenient thing) Not really.
IAmRalsei#3
you didn't explain the first type of DEF well enough.......................................................................................................................................................... help me actually find out how to use the first kind of def to help me create a game about closing your 3DS help me pls
TheV360#4
Replying to:IAmRalsei
you didn't explain the first type of DEF well enough.......................................................................................................................................................... help me actually find out how to use the first kind of def to help me create a game about closing your 3DS help me pls
It said it was unfinished at the end. Also please don't spam new line, it's annoying to scroll through. Here's a quick example:
DEF TEST(A,B$)
 RETURN A+3+LEN(B$)
END

C=TEST(2,"hello world")
PRINT C