From: "marcandre (Marc-Andre Lafortune)" <ruby-core@...>
Date: 2013-04-10T01:17:21+09:00
Subject: [ruby-core:54146] [ruby-trunk - Feature #8229] extend Hash.include?


Issue #8229 has been updated by marcandre (Marc-Andre Lafortune).


Could you elaborate on why this is needed and in which cases one would need this?

Moreover, I would not write `h.include?(key) && h[key] == value`. In most cases `h[key] == value` is sufficient (unless value can be nil or there's a default proc). Otherwise one can write `h.fetch(key, DIFFERENT) == value`, where DIFFERENT is an value different from all possible values of the hash, like Object.new).
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Feature #8229: extend Hash.include?
https://bugs.ruby-lang.org/issues/8229#change-38400

Author: eike.rb (Eike Dierks)
Status: Open
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: Next Major


I'd like to suggest to extend the Hash.include? method.

Currently Hash.include? can only be used to ask for a key,
I believe it should be extended to ask for a (key value) pair.

I believe this extension can be done without breaking prior api.

I suggest to extend the signature of Hash.include?
to Hash.include?(key, value)

That message should return true,
if the receiving object does have an object at key which is equal to value.

It would be a simple replacement for:
    h.include?(key) && h[key] == value

But I do not want to stop there.
I'm heading for h.include_all?(other_hash)
and h.include_any?(other_hash)

and it would be valuable to have h.intersect(other_hash) etc

I believe these to be useful primitives when working with hashes.

I'd like to have the api of the Set class available for the Hash class as well,
but there working on key/value matching.

Obviously any change to such the substantial class as the Hash class
needs a lot of thought for compatibility.

But I believe this can be done without breaking any prior code,
and it could add a lot of new out of the box functionality.

This probably needs some more thought.
We might come up with some dsl like thing like
h.includes.any? or h.includes.all? or h.includes.none?
to be used cross all collection classes.

Someone must be in charge for the Hash class,
my 2p


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