Tuples citizenship

[Jonathan M Davis]

On Thursday, March 01, 2012 18:57:15 bearophile wrote:
> Jonathan M Davis:
> > They also often do poorly when you
> > need to use the functional programming,
> 
> As you know functional languages use tuples all the time.

Yes, but chaining functions is the issue. It doesn't work well with tuples 
unless the function you're passing the result to wants the tuple. If all it 
wants is one piece of the tuple, then that doesn't work well at all. You're 
forced to assign the tuple to something else and then call then function 
rather than chain calls. That's one of the reasons that you constantly end up 
using stuff like let expressions and pattern matching in functional languages. 
You don't _want_ a tuple. Dealing with a tuple is annoying. It's just that 
it's often the best tool that you have to pass disparate stuff around, so 
that's what you use.

> > And if you're not looking to assign the parts of a tuple to
> > existing variables, then they're not quite as bad as when you are, since
> > you don't necessarily have to then assign the pieces to other variables.
> There are parts of your post that I don't fully understand.

It is often really annoying to have to deal with tuple return values, because 
you have to worry about unpacking the result. I don't want to use a tuple in 
the caller. Tuples are generally for grouping unrelated data that you don't 
necessarily want to keep togother (since if you did, you'd generally use a 
struct). I want the result to actually be assigned to variables. That is 
definitely cleaner with out than with tuples.

int exp;
auto result = frexp(value, exp);

vs

auto tup = frexp(value);
result = tup[0];
exp = tup[1];

Getting tuple return values is annoying. Yes, it can be useful, but most stuff 
doesn't operate on tuples. It operates on the pieces of tuples. So, you have 
to constantly break them up. So, using out results in much nicer code.

It always feels like I'm fighting the code when I have to deal with tuple 
return values.

- Jonathan M Davis