Re: Multiple return values

Arthur.Chance@Smallworld.co.uk (Arthur Chance) wrote:


> A thought struck me over the weekend while rereading the "Lambda: the
> Ultimate <foo>" papers:
>
> Most programming languages allow procedures with multiple arguments
> (in some cases allowing them to be used in curried form as well), but
> very few languages allow multiple return values, in spite of the fact
> that multiple results *are* multiple arguments when you're wearing
> CPS-tinted glasses. Why is this?


I think it is an artefact of the origin of the "function" concept. The
idea of a function in maths is that you give it some parameters and it
performs some calculation on them. The result of the calculation is
the return value. It doesn't make sense to have, for example, an
arctangent return more than one value. Given the origins of computing
in maths it is easy to see why this habit has been carried on.


Incidentally, I've been working with an experimental language "Sierra"
which allows multiple inputs and outputs:


define foo =
    (
    in {x, y, z} = integer32
    out {a, b} = boolean16
    ...
    )


The function can still be used in an expression; the idea is that the
parameter list and return values are implicit record structures, so the
expression value can be placed into any variable whose structure matches
the returned values.


-Mars
--

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