Module: SimpleCov::Combine::IdentityInterner

Extended by:
IdentityInterner
Included in:
IdentityInterner
Defined in:
lib/simplecov/combine/identity_interner.rb

Overview

Builds the raw-key => interned-identity caches the tuple combiners keep. A key is mapped on first sight and kept: the pairwise fold would otherwise re-derive the accumulator's identities on every one of its merges, always to the same answer.

Identities exist only to be hash keys, and Array#hash is not memoized, so keying on the identity tuple itself would rehash its elements for every key of both sides of every merge. An Integer hashes as an immediate. Two keys share an id exactly when their identities are equal, so the string and array forms of one key still merge together.

Instance Method Summary collapse

Instance Method Details

#build ⇒ Object 



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# File 'lib/simplecov/combine/identity_interner.rb', line 18

def build
  ids = {} #: Hash[::Array[untyped], Integer]
  Hash.new do |cache, key|
    identity = yield(key)
    cache[key] = ids[identity] ||= ids.size
  end
end