for loops with range range

[david.h...@vidhance.com]

range := 0 .. 5
for (i in range) {
i toString() println()
}

Is this supposed to work?

[Amos Wenger]

looks reasonable, I'd expect it to work.

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[Jeremy Clarke]

I went and added an iterator() method to Range in lang/Numbers.ooc, and then David's code works just fine :)

I was quite surprised about this, because Range is a cover so I couldn't see any way to implement the Iterable class, but it turns out this is not needed.

Should I make a pull request with this in the SDK?

Range: cover {

    min, max: Int

    new: static func (.min, .max) -> This {
        this : This
        this min = min
        this max = max
        return this
    }

    reduce: func (f: Func (Int, Int) -> Int) -> Int {
        acc := f(min, min + 1)
        for(i in min + 2..max) acc = f(acc, i)
        acc
    }
   
    iterator: func -> RangeIterator<Int> {
        RangeIterator<Int> new(this)
    }
   
}

RangeIterator: class <T> extends Iterator<T> {
    i: Int
    range: Range
   
    init: func (=range) {
        i = range min
    }
   
    hasNext?: func -> Bool {
        i < range max-1
    }
   
    next: func -> T {
        i += 1
        i
    }
   
    remove: func -> Bool { false }
}

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Jeremy Clarke

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[Amos Wenger]

rock indeed only checks for the presence of 'iterator' on the type, not if it actually implements the Iterable interface

I think the idea was that for loops should support ranges directly, I'm surprised it doesn't, sounds like something broke (ie. there shouldn't even be a need for RangeIterator).

Is shamanas reading this mailing list?

[Jeremy Clarke]

Ah yes, I thought I was missing something more obvious here, though range variables would take a bit more work to generate a correct for-loop.

Something like   for (int temp = r.min; temp < r.max; temp++) { ... }   in case the range is modified while looping, but yeah I don't know enough about the compiler internals, maybe you guys intended to do that already?

Also I realised I'm an idiot and should've set  i = range min-1   in my previous code. ^^