Computer Science Canada

Default values for function?
Author:  Jay [ Tue Feb 22, 2005 10:58 am ]
Post subject:  Default values for function?
Hey all, I've google'd and searched all this forum, and now I'm finally desperate and posting. Is there any way in Turing to have default values for a function's parameters? I can't find anything that points one way or the other, but I figure if I haven't found anything by now there's probably no way. I also wanted to use function overloading, but found a thread that confirms that that's not possible.

Thanks.
Author:  Tony [ Tue Feb 22, 2005 1:42 pm ]
Post subject: 
there's a way to fake function overload in Turing. You'd have to use pointers to functions and when you want to overload something, just change the pointer to a new function. Should work.

As for default values : there're two approaches to the problem.

1) make all of arguments be string, and if NULL ("") is passed, you make it a default value instead. For integers and floats you can use strint() and strreal().
Turing:

function foo (bar : string) : string
    if bar not= "" then
        result bar
    else
        result "default"
    end if
end foo

put foo ("bar")
put foo ("")


2) Might be a more interesting approach: accepting an array of arguments. The size will be flexable, it is actually possible to incorporate multiple constructors for the same function.. (hardcoded overloading?)
Turing:

function foo (bar : array 0 .. * of string) : string
    var out : array 0 .. 4 of string := init ("1", "2", "3", "4", "5")
    var answer : string := ""
    if upper (bar) not= 0 then %atleast one argument has been passed
        for i : 0 .. upper (bar)
            out (i) := bar (i)
        end for
    end if

    for i : 0 .. upper (out)
        answer += out (i) + " :: "
    end for

    result answer
end foo

var myArguments1 : array 0 .. 0 of string := init ("")
put foo (myArguments1)
var myArguments2 : array 0 .. 1 of string := init ("Tony", "Dan")
put foo (myArguments2)
var myArguments3 : array 0 .. 4 of string := init ("Tony", "Dan", "Martin", "compsci", "Ruby")
put foo (myArguments3)
Author:  Jay [ Tue Feb 22, 2005 4:41 pm ]
Post subject: 
Thanks for the help.

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