SmallBASIC Guide

Subroutines and Functions

Syntax of procedure (SUB) statements

SUB name [([BYREF] par1 [, ...[BYREF] parN)]]
  [LOCAL var[, var[, ...]]]
  [EXIT SUB]
  ...
END

Syntax of function (FUNC) statements

FUNC name[([BYREF] par1 [, ...[BYREF] parN)]]
  [LOCAL var[, var[, ...]]]
  [EXIT FUNC]
  ...
  name=return-value
END

On functions you must use the function's name to return the value. That is, the function-name acts like a variable and it is the function's returned value. The parameters are 'by value' by default. Passing parameters by value means the executor makes a copy of the parameter to stack. The value in caller's code will not be changed. Use BYREF keyword for passing parameters 'by reference'. Passing parameters by reference means the executor push the pointer of variable into the stack. The value in caller's code will be the changed.

' Passing 'x' by value
SUB F(x)
  x=1
END
x=2
F x
? x:REM displays 2

' Passing 'x' by reference
SUB F(BYREF x)
  x=1
END
x=2
F x
? x:REM displays 1

You can use the symbol '@@' instead of BYREF. There is no difference between @@ and BYREF.

SUB F(@@x)
  x=1
END

On a multi-section (PalmOS) applications sub/funcs needs declaration on the main section.

#sec:Main
declare func f(x)

#sec:another section
func f(x)
...
end

Use the LOCAL keyword for local variables. LOCAL creates variables (dynamic) at routine's code.

SUB MYPROC
  LOCAL N:REM LOCAL VAR
  N=2
  ? N:REM displays 2
END

N=1:REM GLOBAL VAR
MYPROC
? N:REM displays 1

You can send arrays as parameters. When using arrays as parameters its better to use them as BYREF; otherwise their data will be duplicated in memory space.

SUB FBR(BYREF tbl)
  ? FRE(0)
  ...
END

SUB FBV(tbl)
  ? FRE(0)
  ...
END

' MAIN
DIM dt(128)
...
? FRE(0)
FBR dt
? FRE(0)
FBV dt
? FRE(0)

Passing & returning arrays, using local arrays.

func fill(a)
  local b, i

  dim b(16)
  for i=0 to 16
    b(i)=16-a(i)
  next
  fill=b
end

DIM v()
v=fill(v)

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