Beyond Ruby

Metorex has these features MRI does not. Each sample below runs under Metorex and prints the output shown. Under MRI each one stops with a NoMethodError at its first call to a method MRI does not have.

Assertions#

assert, assert_equal, and assert_raises are available in every program, with no library to require. A failed assertion raises a RuntimeError. assert_equal's message names the expected value and the value it got.

assert(3.between?(1, 5))
assert_equal(4, 2 + 2)
assert_raises { Integer("four") }

begin
  assert_equal(5, [2, 2].sum)
rescue RuntimeError => failure
  puts failure.message
end

Expected 5, got 4

Finding and Running Test Files#

metorex test DIR runs each file under DIR, or under test/ when no directory is named, named *_test.rb, test_*.rb, or *_spec.rb, reports each one as ok or FAIL with the error that stopped it, and exits with status 1 when one fails. A test file is a program that uses the assertions above.

metorex test

RSpec with No Gems#

Rex, the spec framework built into Metorex, runs suites written for RSpec with metorex spec, and loads the first time a program names RSpec. metorex spec --coverage reports the lines and branches that ran, counted by the interpreter.

Code as Objects#

parse turns source text into the syntax tree nodes Metorex compiles, and body, called on the method get_source returns, answers that method's statements as the same nodes. Each node is a hash with a "type" key. Code as objects goes through them.

def grouped(node)
  case node["type"]
  when "BinaryOp"
    left = grouped(node["left"])
    right = grouped(node["right"])
    "(#{left} #{node["op"]} #{right})"
  when "Grouped" then grouped(node["expression"])
  when "IntLiteral" then node["value"].to_s
  when "Identifier" then node["name"]
  end
end

puts grouped(parse("rate * hours + 40").first)
puts grouped(parse("rate * (hours + 40)").first)

((rate * hours) + 40)
(rate * (hours + 40))