Ethiopian multiplication: Difference between revisions

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@@ Line 1,063: / Line 1,063: @@
 =={{header|Oz}}==
 <lang oz>declare
-  fun {Halve X} X div 2 end
+  fun {Halve X}   X div 2             end
-  fun {Double X} X * 2 end
+  fun {Double X}  X * 2               end
-  fun {Even X} {Abs X mod 2} == 0 end  %% standard function: Int.isEven
+  fun {Even X}    {Abs X mod 2} == 0  end  %% standard function: Int.isEven
   fun {EthiopicMult X Y}
      X >= 0 = true %% assert: X must not be negative
      Rows = for
-               L in X;L>0;{Halve L}
+               L in X; L>0;  {Halve L}  %% C-like iterator: "Init; While; Next"
-               R in Y;true;{Double R}
+               R in Y; true; {Double R}
-               collect:C
+               collect:Collect
-            do
+	    do
-               {C L#R}
+	       {Collect L#R}
-            end
+	    end
-     OddRows = {Filter Rows fun {$ L#_} {Not {Even L}} end}
+     OddRows = {Filter Rows LeftIsOdd}
+     RightColumn = {Map OddRows SelectRight}
   in
+     {Sum RightColumn}
-     {FoldL OddRows fun {$ Z _#R} Z+R end 0}
   end
+  %% Helpers
+  fun {LeftIsOdd L#_}   {Not {Even L}}          end
+  fun {SelectRight _#R} R                       end
+  fun {Sum Xs}          {FoldL Xs Number.'+' 0} end
 in
   {Show {EthiopicMult 17 34}}</lang>