I was thinking something like
struct Foo { x: int, y: int }
fn f(foo: &mut Foo) {
(foo.x, foo.y) = g();
}
(I actually get an ICE building this (with with appropriate g() and main())
using rustc 0.8 eb55348.)
I kind of like this idea of letting arbitrary lvalues appear in the "variable"
position in pattern syntax. But I don't know if it would turn out to be a can
of worms.
keegan
----- Original Message -----
From: "Matthew McPherrin" <[email protected]>
To: "Benjamin Striegel" <[email protected]>
Cc: [email protected]
Sent: Wednesday, September 25, 2013 12:10:29 PM
Subject: Re: [rust-dev] Some suggestions of Rust language
Maybe if you were writing code like this:
let mut a = 1; let mut b = 2;
loop {
...
(a, b) = F();
...
}
(b, a)
On Wed, Sep 25, 2013 at 11:29 AM, Benjamin Striegel
<[email protected]> wrote:
> Is there a use case that necessitates such a feature? The following code
> works today:
>
> let a = 1;
> let b = 2;
> let (a, b) = (b, a);
>
> Not sure why that wouldn't be sufficient.
>
>
> On Wed, Sep 25, 2013 at 2:50 PM, Marvin Löbel <[email protected]>
> wrote:
>>
>> On 09/25/2013 06:37 PM, Diggory Hardy wrote:
>>>
>>> Hi,
>>>
>>> On Wednesday 25 September 2013 08:29:17 Patrick Walton wrote:
>>>>
>>>> On 9/25/13 6:32 AM, Alexander Sun wrote:
>>>>>
>>>>> Multiple return values
>>>>> if has a function like this:
>>>>>
>>>>> fn addsub(x : int, y : int) -> (int, int) {
>>>>>
>>>>> return (x+y,x-y);
>>>>>
>>>>> }
>>>>>
>>>>> them, this is valid:
>>>>>
>>>>> let (b,c) = addsub(x, y);
>>>>>
>>>>> but this is invalid;
>>>>>
>>>>> let b:int =0;
>>>>> let c:int =0;
>>>>> (b,c) = addsub(x, y);
>>>>>
>>>>> also invalid:
>>>>>
>>>>> let (b,c) = (0, 0);
>>>>> (b,c) = addsub(x, y);
>>>>
>>>> If we did this, we wouldn't know whether to parse a pattern or an
>>>> expression when starting a statement. This isn't fixable without trying
>>>> to define some sort of cover grammar that covers both expressions and
>>>> patterns, like ECMAScript 6 does. I don't know if this would work in
>>>> Rust.
>>>
>>> Are there any plans to support something like:
>>>
>>> assign (b,c) = addsub(x,y);
>>>
>>> for existing b,c? The best I could come up with is:
>>>
>>> match two_nums(2) {
>>> (x,y) => {a=x;b=y;}
>>> }
>>>
>>> Not that I need this; just curious.
>>
>> I had the idea once to reuse the `in` keyword for that:
>>
>> let mut a = 0; let mut b = 1;
>> in (a, b) = (b, a);
>>
>> No idea how feasible that would be, though.
>>
>> _______________________________________________
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>> [email protected]
>> https://mail.mozilla.org/listinfo/rust-dev
>
>
>
> _______________________________________________
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>
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