Implement ADD, MULTIPLY and POWER for natural numbers

tomstuart · Oct 17, 2011 · 3bf39f9c9913ad568cbdae075966cc9c4dd25984 · 3bf39f9
1 parent 29e4596
commit 3bf39f9c9913ad568cbdae075966cc9c4dd25984
Unified Split

Showing with 6 additions and 6 deletions.

+3 −3 lib/nothing.rb

+3 −3 spec/nothing_spec.rb
diff --git a/lib/nothing.rb b/lib/nothing.rb
@@ -9,9 +9,9 @@ module Nothing
  TIMES     = -> n { -> f { -> x { n[f][x] } } }
  INCREMENT = -> n { -> f { -> x { f[n[f][x]] } } }

-  # ADD       =
-  # MULTIPLY  =
-  # POWER     =
+  ADD       = -> m { -> n { n[INCREMENT][m] } }
+  MULTIPLY  = -> m { -> n { n[ADD[m]][ZERO] } }
+  POWER     = -> m { -> n { n[MULTIPLY[m]][ONE] } }
  # DECREMENT =
  # SUBTRACT  =

diff --git a/spec/nothing_spec.rb b/spec/nothing_spec.rb
@@ -11,9 +11,9 @@

    specify { TIMES[representation_of 3][-> s { s + 'o' }]['hell'].should == 'hellooo' }
    specify { INCREMENT[representation_of 2].should represent 2 + 1 }
-    specify { pending { ADD[representation_of 2][representation_of 3].should represent 2 + 3 } }
-    specify { pending { MULTIPLY[representation_of 2][representation_of 3].should represent 2 * 3 } }
-    specify { pending { POWER[representation_of 2][representation_of 3].should represent 2 ** 3 } }
+    specify { ADD[representation_of 2][representation_of 3].should represent 2 + 3 }
+    specify { MULTIPLY[representation_of 2][representation_of 3].should represent 2 * 3 }
+    specify { POWER[representation_of 2][representation_of 3].should represent 2 ** 3 }
    specify { pending { DECREMENT[representation_of 3].should represent 3 - 1 } }
    specify { pending { SUBTRACT[representation_of 3][representation_of 2].should represent 3 - 2 } }