Feature #8229: extend Hash.include?

• Status: Assigned
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[eike.rb (Eike Dierks)]

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

[naruse (Yui NARUSE)]

• Description updated (diff)
• Category changed from misc to core
• Assignee changed from nobu (Nobuyoshi Nakada) to matz (Yukihiro Matsumoto)

[nobu (Nobuyoshi Nakada)]

• File 0001-hash.c-Hash-include-improve.patch 0001-hash.c-Hash-include-improve.patch added

One ticket, one feature, please.

[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).

[headius (Charles Nutter)]

As a feature that affects all Ruby implementations, this should probably move to CommonRuby: https://bugs.ruby-lang.org/projects/common-ruby

[fuadksd (Fuad Saud)]

I think this would be more interesting if in the form:

h = { a: 'b', c: { d: 'e' } }

h.include?({c: { d: 'e' } }) # => true

It would accept a hash and check whether h includes that hash.

[naruse (Yui NARUSE)]

• Target version deleted (3.0)

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Assigned