Simplest way to convert an array into a set

H. S. Teoh hsteoh at
Mon Feb 13 18:48:47 UTC 2023

On Mon, Feb 13, 2023 at 06:04:40PM +0000, Matt via Digitalmars-d-learn wrote:
> Obviously, there is no "set" object in D,

Actually, bool[T] could be used as a set object of sorts. Or even
void[0][T], though that's a little more verbose to type. But this can be
aliased to something nicer (see below).

> but I was wondering what the quickest way to remove duplicates from an
> array would be. I was convinced I'd seen a "unique" method somewhere,
> but I've looked through the documentation for std.array, std.algorithm
> AND std.range, and I've either missed it, or my memory is playing
> tricks on me. That, or I'm looking in the wrong place entirely, of
> course

Try this:

import std;
auto deduplicate(R)(R input)
	if (isInputRange!R)
	alias Unit = void[0];
	enum unit = Unit.init;
	Unit[ElementType!R] seen;
	return input.filter!((e) {
		if (e in seen) return false;
		seen[e] = unit;
		return true;
unittest {
	assert([ 1, 2, 3, 4, 2, 5, 6, 4, 7 ].deduplicate.array ==
		[ 1, 2, 3, 4, 5, 6, 7 ]);
	assert([ "abc", "def", "def", "ghi", "abc", "jkl" ].deduplicate.array ==
		[ "abc", "def", "ghi", "jkl" ]);


Маленькие детки - маленькие бедки.

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