[swift-evolution] [DRAFT] Regularizing Where Grammar (was Re: Add a while clause to for loops)

[Thorsten Seitz]

-1

> Am 10.06.2016 um 21:10 schrieb Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org>:
> 
> if case .some(let Point.cartesian(x, y)) where x < y = json["rect"]?["origin"].flatMap(.init(rawValue:)) { … }

This: `where x < y = json[…]` is *very* unreadable and probably unparseable as it is missing a delimiter between the boolean expression and the expression behind the assignment operator. And I do not count the assignment operator as a sufficient delimiter.


I’ll give the following counterargument against this shuffling around of `where` or trying to eliminate it:

	if case .some(let x) = someExpression where x > 0

	for x in xs where x > 0

These are actually very consistent in their grammar when you look at it like follows:

	<target> <assignment op> <source> where <condition>


	if case .some(let x) = someExpression where x > 0

	target: `case .some(let x)`
	assignment op: `=`
	source: `someExpression`
	condition: `x > 0`


	for x in xs where x > 0

	target: `x`
	assignment op: `in`
	source: `xs`
	condition: `x > 0`


That is I’m arguing the `where` grammar is already quite regular and should not be changed. And yes, I’d like to have `where` back in `case`. And `let`.

-Thorsten

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