FUNCTION RETURN STATEMENT

▶ FUNCTION RETURN STATEMENT

Function return statements are used when the execution of the enclosing function needs to be stopped immediately, and a result has to be returned to the function caller.

To make a function return statement, write:

%% num

Tyl symbolizer will replace the double percent code '%%', with '✖✖', the function break symbol:

✖✖ num

Consider this program:

go:

maxnumresult maxnum 2 3

print maxnumresult

maxnum num1 num2:

num2 > num1 ? ✖✖ num2

num1

maxnum function gets two numbers and returns the greater of them. If num2 is greater than num1, the function return statement '%% num2', will be executed, maxnum function running will stop, and num2 will be returned, otherwise, the code will continue to line num1, and that will be the returned value of the function.

Generally, function return statement is used to return values before function end.

This is a key value mapping (hashmap) implementation:

go:

citycode 4524

city citymap citycode

city ? print 'selected city: (' + citycode + ') ' + city

citymap key:

key 1491 ? ✖✖ 'Tokyo'

key 2502 ? ✖✖ 'Timboktu'

key 3513 ? ✖✖ 'Tallahassee'

key 4524 ? ✖✖ 'Thule'

selected city: (4524) Thule

citymap is a mapping function, that returns a value for key. It is composed of conditional statements with function return statement as their yes block.

The return statement can be any statement. Consider this:

go:

num 20

i 4 ~ print addbystep ( num -- 4 ) 10

addbystep num step:

num > step ? %% addtwo num

addone num

addone num: num + 1

addtwo num: num + 2

18
14
9
5

addbystep function return statement is an operation on num, based on step parameter. In the looping statement 'i 4 ~', num variable of go function is decremented by 4, using the double minus operator '--', and is fed to addbystep along with a fixed step 10. As long as num is greater then step, addbystep returns the result of addtwo num, otherwise the result of addone num.