Unify needle overloads of std.algorithm.searching.find

[wilzbach]

First step at allowing partial instantiation of find (I will try to keep the PRs small) - more work to follow soon.

This PR groups three overloads into one overload. As discussed so often - a user shouldn't need to know about internal performance optimization, so this should be valuable regardless.

See: #5497 (comment)

CC @CyberShadow @andralex

[dlang-bot]

Thanks for your pull request, @wilzbach!

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[CyberShadow]

Thanks for working on this!

Here's some use cases / examples / unit tests I wrote:

///
@safe unittest
{
    import std.functional : not;
    import std.ascii : isWhite;

    // Skip whitespace at the front of a string
    alias skipWhitespace = find!(not!isWhite);
    assert("  Hello".skipWhitespace == "Hello");
}

///
@safe unittest
{
    import std.uni : toLower;

    // Case-insensitive find
    alias ifind = find!((a, b) => toLower(a) == toLower(b));
    assert(ifind("Hello World", "OR") == "orld");
}

[wilzbach]

Here's some use cases / examples / unit tests I wrote

Thanks - I will keep them in mind, but I think I am still two or three PRs away from the eponymous conversion of find. Well, let's see and go step by step :)

[wilzbach]

Well, let's see and go step by step

Urgh - I just realized that I have done this before: #5150 :/

[andralex]

nicely done thx