FUNCTION...END FUNCTION

FUNCTION ... END FUNCTION


    FUNCTION name ( [arg [= expr]{,arg [= expr]} ] [, ...] )
        [ DIM variable {, variable } ]
        [ STATIC variable {, variable } ]
        [ SHARED variable {, variable } ]
        [ RETURN expr {, expr} ]
        [ EXIT FUNCTION ]
        { statement }
    END FUNCTION

Define a function. Unlike many BASICs, more than one value may be returned from a function. As a result, the Return keyword is used to return values from functions. If no value is explicitly returned, the value Nothing is returned.


    FUNCTION addOne( n )
        RETURN n + 1
    END FUNCTION

You can have optional values in parameters. If these parameters are are not included in the function call, they are assigned the default value:


    FUNCTION hasOptional( a, b=10, c="default string" )
        PRINT "a=", a
        PRINT "b=", b
        PRINT "c=", c
    END FUNCTION

You can use Static variables in functions. These are variables that retain their value. The initial value of Static variables is Nothing:


    FUNCTION accum( n )
        ' declare result as a STATIC variable
        STATIC result

        ' first time calling accum?
        IF result = NOTHING THEN
            ' initialize the result
            result = n
        ELSE
            ' add value to the result
            result = result + n
        END IF

        ' return accumulated result
        RETURN result

    END FUNCTION

Some or all of the return values may be discarded by the caller. If a function returns more values than requested, the extra values are discarded. If the function returns less values than expected, the extra variables are assigned the value Nothing:


    FUNCTION returnThreeValues()
        RETURN 1, 2, 3
    END FUNCTION

    ' ignore all values
    returnThreeValues()

    ' ignore the last value
    a, b = returnThreeValues

    ' Nothing is assigned to d
    a, b, c, d = returnThreeValues()

index function;