Implement a multimap

[steveklabnik]

Issue by treeman
Monday Jul 14, 2014 at 20:12 GMT

For earlier discussion, see rust-lang/rust#15669

This issue was labelled with: A-libs, I-enhancement in the Rust repository

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Extensions to treemap and hashmap, with set variations. Indicated by the wiki.

[carycodes]

It looks like there's a pretty decent go at this already at https://github.com/havarnov/multimap
(Note: that's not me.)

[cflewis]

Should this be closed?

[codeyash]

Please No. I don't want to use external. If rust provides and supports or even merge this project then we can use it. external crate may die anytime as mostly one guy support so for core features like this one there should be some internal support. Almost all langs supports this.

[eddyb]

cc @rust-lang/docs Perhaps it would be useful to have, somewhere in a FAQ, an explanation of how external crates are not bound to be of worse quality and less maintained than libstd proper?
Or if there is one already, could you link it here?

[sfackler]

@codeyash Are you sure "almost all langs" do in fact support that? None of Python, D, Java, Ruby, Go, PHP, Javascript, Perl, or Swift provide multimaps in their standard libraries.

[codeyash]

@sfackler yes almost all is incorrect but I was talking about langs like C++, Scala and Qt

[eternaleye]

@codeyash: Qt is not a language; it's a library written in C++. A Rust equivalent would be on crates.io, not in the stdlib; just as Qt is available as a separate package, and not as part of libstdc++, libc++, or the Microsoft C++ standard library implementation.

On the other hand, in Rust, a library like Qt would almost certainly be split out into multiple crates; much as Qt has been splitting itself first into separate libraries for different functionalities (Qt 3 -> Qt 4) and then further into separately-installable packages (Qt 4 -> Qt 5).

In short: If you don't find using Qt for its multimap objectionable in the C++ world, there is no defensible reason to object to using a Cargo crate for it in the Rust world. (Heck, Rust makes it easier, because we have a powerful dependency manager that C++ lacks. Getting Qt set up for development can be painful unless you either use a distro package or use a Qt-themed development environment.)