New names - 2.068 roundup

[John Colvin via Digitalmars-d]

On Wednesday, 24 June 2015 at 01:04:01 UTC, Adam D. Ruppe wrote:
> We disagreed on this on irc, but I ask you to consider the 
> following which limits the code breakage a lot more than my 
> first proposal in chat:
>
> ---
>
> import std.range;
>
> struct ToLowered(R) if(isInputRange!R) {
> 	R inputRange;
> 	this(R r) {
> 		static if(isForwardRange!R)
> 			inputRange = r;
> 		if(!empty)
> 			front = cast(char) (inputRange.front | 0x20);
> 	}
>
> 	char front;
>
> 	static if(isForwardRange!R)
> 	typeof(this) save() { return this; }
>
> 	bool empty() {
> 		return inputRange.empty();
> 	}
>
> 	void popFront() {
> 		inputRange.popFront();
> 		if(!empty)
> 			front = cast(char) (inputRange.front | 0x20);
> 	}
>
> 	private immutable(char)[] eagerCache;
> 	deprecated("please call .array on this yourself or adjust your 
> algorithm to use the laziness (tip: changing string 
> declarations to auto may help)")
> 	string eager() pure {
> 		if(eagerCache is null) {
> 			foreach(c; this)
> 				eagerCache ~= c;
> 		}
> 		return eagerCache;
> 	}
>
>  	alias eager this;
> }
>
> ToLowered!R toLower(R)(R r) {
> 	return ToLowered!R(r);
> }
>
>
> void main() {
> 	import std.stdio;
>
> 	string s = "Amazing Stuff".toLower; // alias this!
> 	writeln(s);
>
> 	string[string] lol;
> 	lol["FOO"] = "FOO".toLower; // alias this!
>
> 	writeln(lol);
> }
>
> ---
>
>
> The code breakage is minimal (especially if we don't actually 
> deprecate that eager method) - cases where a string is expected 
> is automatically handled by the alias this, and pipelines using 
> auto will just work. Copying this struct has the same semantics 
> as copying the string The change of type can break code - but 
> only code that was neither quite static nor quite generic.
>
> Code that statically takes a string works, as will returning a 
> string, that's also covered by alias this. Code that 
> generically works on input/forward ranges works, as this is 
> still a by-value forward range. Only code that takes a template 
> argument and literally checks if(is(T == string)) or 
> if(is(isArray!T)) and those variants will break on this.
>
>
>
> I confess, that is some code, but with alias this, we have a 
> migration path to change a lot of usages of the existing 
> functions to be lazy without dreaming up new names.
>
> Moreover, with this, some old code will *automatically* be 
> upgraded to laziness without needing to change at all too. Tell 
> me that doesn't at least tempt you!

Yup, mind completely blown.

I almost want to put "alias eager this;" in all my ranges now...