CustomEnumerable module

custom_enumerable.rb

module CustomEnumerable
  def map(sym = nil)
    return enum_for(:map) if !block_given? && sym.nil?
    raise SyntaxError if block_given? && !sym.nil?
    result = []
    each do |item|
      result << (sym.nil? ? yield(item) : item.send(sym))
    end
    result
  end

  def find(sym = nil)
    return enum_for(:find) if !block_given? && sym.nil?
    raise SyntaxError if block_given? && !sym.nil?
    each do |item|
      return item if sym.nil? ? yield(item) : item.send(sym)
    end
    nil
  end

  def reduce(initial_or_sym, sym = nil)
    if initial_or_sym.is_a?(Symbol)
      operator = initial_or_sym
      initial = nil
    else
      initial = initial_or_sym
      operator = sym
    end
    accumulator = initial
    each_with_index do |item, index|
      if index.zero? && initial.nil?
        accumulator = item
        next
      end
      accumulator = operator.nil? ? yield(accumulator, item) : accumulator.send(operator, item)
    end
    accumulator
  end
end