Question

Why do functions in some popular languages return only a single type of result?

i.e I mean Why The Compilers give Error on Following Syntax

public int int  returnTwoIntegers(){
.......
........
}

Answer 1

Daniel Weinreb — who worked on both Lisp dialects (which had multiple return values) and Java (which didn’t), explains why:

When we added the multiple-value return feature to Lisp machine Lisp (from whence it went into Common Lisp), I believe that the desire to avoid consing was one of the serious motivations. Back then, we did not have good GC technology, and writing Lisp programs to carefully minimize consing was very common.

The other reason was for expressiveness: to make it clear that the function was really returning more than one result, rather than introducing a little list “type” (e.g. “a two-list of the file handle and a boolean to say whether…”).

In Java, I’ve seen definitions of little classes whose only purpose is to be a way to return multiple values. The advantage of this approach is that the types and meanings of the returned values are documented (at least if you pick clear names and put in comments!). But it’s rather verbose, in my opinion.

When I was first reviewing the early Java spec, I was surprised to see that there was no way to return multiple values. I wanted to lobby for adding that, so I tried to come up with a use case that was both simple and very compelling. I was unable to do so! So I didn’t try lobbying for it. The designers of Java were pretty clearly trying to avoid a lot of bells and whistles (and syntactic sugar), and there’s certainly a lot to be said for that.