Add support code for specs

spec/spec_helper.rb

@@ -0,0 +1,8 @@
+require 'nothing'
+require 'support/pair'
+require 'support/helpers'
+require 'support/matchers'
+
+RSpec.configure do |c|
+  c.include Helpers
+end

spec/support/ffi.rb

@@ -0,0 +1,76 @@
+require 'nothing'
+require 'support/pair'
+
+module Nothing
+  module FFI
+    def to_integer(n)
+      TIMES[n][-> integer { integer + 1 }][0]
+    end
+
+    def from_integer(integer)
+      n = ZERO
+
+      integer.times do
+        n = INCREMENT[n]
+      end
+
+      n
+    end
+
+    def to_boolean(b)
+      IF[b][true][false]
+    end
+
+    def from_boolean(boolean)
+      if boolean then TRUE else FALSE end
+    end
+
+    def to_pair(p)
+      Pair.new(LEFT[p], RIGHT[p])
+    end
+
+    def from_pair(pair)
+      PAIR[pair.left][pair.right]
+    end
+
+    def to_array(l)
+      array = []
+
+      until to_boolean(IS_EMPTY[l])
+        array.push(FIRST[l])
+        l = REST[l]
+      end
+
+      array
+    end
+
+    def from_array(array)
+      l = EMPTY
+
+      until array.empty?
+        l = UNSHIFT[l][array.last]
+        array.pop
+      end
+
+      l
+    end
+
+    CHARSET = '0123456789BFiuz'.chars.entries # for encoding digits, "Fizz" and "Buzz"
+
+    def to_char(c)
+      CHARSET.at(to_integer(c))
+    end
+
+    def from_char(char)
+      from_integer(CHARSET.index(char))
+    end
+
+    def to_string(s)
+      to_array(s).map { |c| to_char(c) }.join
+    end
+
+    def from_string(string)
+      from_array(string.chars.map { |char| from_char(char) })
+    end
+  end
+end

spec/support/helpers.rb

@@ -0,0 +1,25 @@
+require 'support/ffi'
+require 'support/pair'
+
+module Helpers
+  include Nothing::FFI
+
+  def representation_of(value)
+    case value
+    when Integer
+      from_integer value
+    when TrueClass, FalseClass
+      from_boolean value
+    when Pair
+      pair = Pair.new(representation_of(value.left), representation_of(value.right))
+      from_pair pair
+    when Array
+      array = value.map { |v| representation_of v }
+      from_array array
+    when String
+      from_string value
+    else
+      fail "don't know how to represent #{value.inspect}"
+    end
+  end
+end

spec/support/matchers.rb

@@ -0,0 +1,28 @@
+require 'support/ffi'
+
+RSpec::Matchers.define :represent do |value|
+  include Nothing::FFI
+
+  def represents?(representation, value)
+    case value
+    when Integer
+      to_integer(representation) == value
+    when TrueClass, FalseClass
+      to_boolean(representation) == value
+    when Pair
+      pair = to_pair(representation)
+      represents?(pair.left, value.left) && represents?(pair.right, value.right)
+    when Array
+      array = to_array(representation)
+      (array.length == value.length) && array.zip(value).all? { |r, v| represents?(r, v) }
+    when String
+      to_string(representation) == value
+    else
+      fail "don't know how to represent #{value.inspect}"
+    end
+  end
+
+  match do |representation|
+    represents?(representation, value)
+  end
+end

spec/support/pair.rb

@@ -0,0 +1 @@
+Pair = Struct.new :left, :right