Yes, I was thinking something similar yesterday. Such a pattern might well be
perfect.
On Nov 14, 2011, at 11:40 PM, David Rajchenbach-Teller wrote:
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> On 11/15/11 12:47 AM, Niko Matsakis wrote:
>>
>> On Nov 14, 2011, at 12:53 PM, Brian Anderson wrote:
>>
>>> std has a 'result::t<T, U>' type that I am trying to use for this
>>> purpose. std::io makes use of this now.
>>
>> Besides exceptions, I do not have a better alternative than
>> `std::result`. However, I fear that if we go too far down this
>> style, it will very painful and we will find ourselves wishing for
>> syntactic sugar to support chaining (whether that is monads or
>> something else). At least this has been my experience when working
>> in OCaml.
>>
>> Are we sure that we do not want exceptions?
>
> Actually, since we have `ret`, I'm sure that we can have small
> syntactic sugar without resorting to monads.
>
> Assuming we have,
>
> foo(x: str) -> result::t<T, U> { ... }
>
> We could write
>
> let x = #result[foo(y)]
>
> And expand it to
>
> let x = {
> let __result = foo(y);
> alt(__result) {
> ok(z) { z }
> err(_){
> //Possibly add some logging here
> ret __result
> }
> }
> }
>
> In practice, this is already what happens in mozilla-central. Not
> ideal, but probably easier to sell to non-fp users as monads, and it
> takes advantage of `ret`. I wonder about performance, though. Is there
> a way that the compiler could recognize this pattern and somehow
> optimize it to attain the same kind of performance as exceptions?
>
> Cheers,
> David
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