findSplitBefore/After should have needle-less overloads

[dlangBugzillaToGithub]

jakobovrum (@JakobOvrum) reported this on 2013-08-30T23:26:46Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=10933

CC List

• bugzilla (@WalterBright)
• luis

Description

`find` has an overload that doesn't take a needle but requires an unary predicate function. `findSplitBefore` and `findSplitAfter` should have equivalent overloads.

Test illustrating use:

----
unittest
{
	import std.algorithm : findSplitBefore;
	import std.uni : isWhite;
	import std.string : stripLeft;

	immutable tests = [
		"prefix postfix lorem ipsum",
		"prefix\tpostfix lorem ipsum"
	];

	foreach(test; tests)
	{
		auto result = test.findSplitBefore!isWhite();
		assert(result[0] == "prefix");
		assert(result[1].stripLeft() == "postfix lorem ipsum");
	}
}
----

It would be especially useful because `until` is strictly lazy and thus can't be used with slicing to reproduce the above results.

[dlangBugzillaToGithub]

luis commented on 2018-03-21T18:25:16Z

Yup, I've ran into the same issue multiple times. This last time with the plain findSplit; I don't recall if also with findSplitBefore/After.

This workaround works:

range.byCodeUnit.findSplit!((a, b) => a.isWhite)(" ");

Interestingly, if you use "" instead of " " it won't work, which arguably is a bug, since the predicate doesn't even use b.