[swift-evolution] Reduce with inout

[Jeremy Pereira]

> On 18 Jan 2017, at 02:17, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> A serious possibility would be: `reduce(mutableCopyOf: x) { ... }`.
> 
> It's verbose, but the nicer-looking `reduce(mutating: x) { ... }` is incorrect since, as Charles pointed out to Dave, it's not `x` that's mutated but rather a mutable copy of it, so it doesn't matter if `x` itself is declared with `let` or `var`.

Why not also have that version?

var foo = 0
let bar: [SomeType] = ...

bar.reduce(mutating: &foo, someFunction) 

// foo now contains the reduced bar


> 
> 
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