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A function that passes tuples, or multiple arguments as they are more commonly referred to as, is not particularly weird, and has pretty much been the norm since the addition of functions to programming languages. But you are right that languages whose functions only accept tuples, but not return tuples, is a strange curiosity. In practice, you end up with developers packing multiple, unrelated items into a single variable to work around the limitation, which then questions why not do the same for input?

▲ the_gipsy 21 hours ago | parent [-]

I meant weird/useless in the sense of that it's used virtually nowhere in practice.

There is a nice func Must(value, err) { if err { panic(err) } else { return value } that you can use in tests to get around the inane regular error handling. But that's about it, to my knowledge. Sad that there isn't more to it. If literally everything returns error as last return value, there could well be some syntax sugar there.

▲ 9rx 20 hours ago | parent [-]

I see it used often, even in languages that don't formally support multiple return arguments – with some hacked up array/object single value return to try and emulate what would be better represented as multiple return arguments.

Like I mentioned in another comment, Go does seem especially prone to attracting developers familiar with other languages who insist on trying to continue to program in those other languages even after working in a Go codebase. That may create a condition whereby the developers you regularly come across don't have a good grasp of where to use multiple return arguments effectively, and thus end up avoiding them, even where they would be appropriate.

With respect to the syntax sugar, there have been a number of proposals for exactly that. While the proposed syntax itself has been well received, nobody has come up with a good solution for the rest of the problem. Syntax is only about 10% of what is needed, of course. Rust, for example, has well defined traits and other features to go along with its '?' operator to fill in the remaining 90%. Presumably there is a good solution out there for Go too, but until someone proposes it...

▲ the_gipsy 11 hours ago | parent [-]

The pragmatically "right" choice is to have some tuple type built-in. Because they are not only very good for function in/out, they can be used in many more places. Lists of tuples, tuples in structs, etc.

If the language doesn't have tuples, then you have to "roll your own" and emulate them every single time, but it's not a functor so you can't do all the useful stuff.

Go didn't do the pragmatically right choice, because it's only right from a type perspective. But go doesn't care about types at all, they're just a side effect. Go only needed to return multiple values, so that you don't have to pass in one (or more) "out" pointer as argument, and check an errnum. So go is right but only from its narrow perspective: it's better than C.

▲ 9rx 8 hours ago | parent [-]

> The pragmatically "right" choice is to have some tuple type built-in.

Perhaps, but in practice we end up with these ill-conceived languages that support tuples but end up not embracing them. Consider, for example, this Rust function:

   fn process_tuples(tuple1: (i32, i32), tuple2: (i32, i32), tuple3: (i32, i32))

If it made the "right" choice a function would only accept a single input value, which could be a tuple:

   fn process_tuples(tuples: ((i32, i32), (i32, i32), (i32, i32)))

But maybe that's not actually the "right" choice? What if there is a pragmatic reason for functions to have their own concept for tuples that is outside of a tuple type? I will admit, I would rather work with the former function even if it is theoretically unsound. It does a much better job of communicating intent, in my opinion.

And once you accept the theoretical unsoundness of a function having its own tuple concept for input, it naturally follows that it needs to also extend that concept to returns. After all, the most basic function is an identity function. What would be super weird is not being able to write an identity function any time the number of inputs is greater than one.

Go needed to allow multiple outputs because functions can accept multiple inputs.

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the_gipsy 5 hours ago | parent [-]

> Go needed to allow multiple outputs because functions can accept multiple inputs.

I don't think that's the right conclusion, unless you have any source or insight?

It would explain why you can directly cast the multi-return-values into parameters when calling, but... that doesn't seem to fit go at all.

What I would think is that "go needed multi-return to be able to return errors along values", and the mentioned feature is just some vestige. It's not like go ever implements anything for the sake of consistency or correctness.

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9rx 2 hours ago | parent [-]

> I don't think that's the right conclusion

It is the "right" conclusion in general. Multiple input arguments without multiple output arguments is frustratingly awkward. I can understand the appeal of your suggestion of only accepting one input and returning one output, where the passed value might be a tuple, but I expect there is good, pragmatic reason why virtually no languages, even those with a proper tuple type, haven't gone down that road. Once a language accepts multiple arguments, though, it needs them in and out. Otherwise you can't even write an identity function. If you can't write an identity function, is it even a function?

> "go needed multi-return to be able to return errors along values"

If there was some specific reason for its addition, beyond the simple fact that it would be crazy not to, it was no doubt for map presence checks. Without that, it is impossible to know if a map contains a given key. Errors can be dealt with in other ways. It wouldn't strictly be needed for that purpose, although it turns out that it also works for that purpose, along with a whole lot of other purposes. Not to mention that we know that the error type was a late-stage addition, so there is strong evidence that errors weren't a priority consideration in the language design.

	▲	the_gipsy 15 minutes ago \| parent [-]
		With conclusion I meant you claiming that go returns multiple values because a function also takes multiple values. I did not refer to judging this as worse or better than having tuples as general types instead. > it was no doubt for map presence checks. Without that, it is impossible to know if a map contains a given key Are you just making stuff up on the go? A map access is not even a function call. And if you need a presence check in the early language development stage, it's much simpler to add support to check presence and then get the value, since it's not threadsafe anyway.