module Enumerable

Returns a hash { key => element }, where key is the value returned by the block when passed element.

Raises an exception if two elements return the same key.

Examples:

%w(a bb ccc).keyed_by(&:length)  #=>  {1 => 'a', 2 => 'bb', 3 => 'ccc'}
%w(a bb cc).keyed_by(&:length)   #=>  RuntimeError "duplicate key: 2"

# File lib/sublime_dsl/core_ext/enumerable.rb, line 14
def keyed_by
  h = {}
  each do |element|
    key = yield(element)
    h.key?(key) and raise "duplicate key: #{key.inspect}"
    h[key] = element
  end
  h
end