On 20.04.2016 23:27, Slava Pestov wrote:
On Apr 19, 2016, at 10:54 AM, Haravikk via swift-evolution
<[email protected] <mailto:[email protected]>> wrote:
* Possibly optimisations unavailable to Array passing?
Indeed, it should be possible to implement varargs by allocating the
argument array on the stack (and having the compiler implicitly copy it to
the heap inside the callee if it escapes). Although you can imagine this
type of optimization being performed for arbitrary arrays, it would be more
difficult and less predictable.
But what about situations when we need to pass an array to function that
accepts only variadic params? Don't we need some #splat() function?
Slava
*Cons*:
* Doesn’t do anything that passing an array directly can’t.
* Passing an array is actually slightly more flexible (can dynamically
pass more or less arguments as required at the call site).
* Less explicit type at call site; gives the appearance of passing
instance(s) of Foo, rather than one instance of [Foo], can lead to
ambiguity with overloaded functions.
* Extra syntax to support (enabling array passing would be more code
required to support this feature)
I’d also argue that variadic functions increase the learning curve, as
the first time you’re presented with one it isn’t necessarily clear what
it does unless you’ve encountered them before. Like I say it can be
ambiguous at the call-site in particular, as it doesn’t show that an
array of [Foo] is being passed as opposed to N instances of Foo (however
many are in the call).
While I’ve used them in the past, I’ve never really felt that they
simplify anything enough to justify them, as it’s just two square
brackets extra to pass an array; this is extra noise sure, but clarifies
what is actually happening.
So if variadic functions don’t have any other advantages, then it’s
really just a very minor piece of syntactic sugar that can lead to more
confusion, less explicit types in function calls, an extra piece of
syntax to parse and handle and possibly other features required to
support it better (like the one being inquired about). The only other
argument I can think of for them is that many other languages have them,
but that’s not important to me vs cutting out cruft.
Short version; removing variadic functions would solve the problem of
defining overloads for both variadic and array types by only ever
requiring the latter.
P.S- I’d also like to note that where possible people should be accepting
Sequences or Collections in their methods anyway rather than arrays
specifically, as it’s more flexible that way ;)
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