Open Radar

 
Summary:
`find` takes a Collection of Equatable Elements and an example Element and returns the index of the first one which is equal to the passed Element. This is valuable as an `indexOf` case, but it would be more valuable for it to take a predicate instead of an element (or for an overload to exist which does this.

For example:

func find<C : Swift.Collection>(domain: C, predicate: C.GeneratorType.Element -> Bool) -> C.IndexType? {
	for index in domain.startIndex..<domain.endIndex {
		if predicate(domain[index]) { return index }
	}
	return nil
}

This returns the index of the first member of the collection for whom the predicate returns `true`, or else it returns `nil`.

I can use this `find` to do a linear search through an array of tuples looking for one whose first element is equal to something, whereas the existing one won’t work for two reasons:

1. Tuples aren’t Equatable
2. I want to match only on the tuple’s first element, not the whole tuple


Steps to Reproduce:
N/A


Expected Results:
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Actual Results:
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Regression:
N/A


Notes:
<3