Data commit

Task/Knuth-shuffle/Lambdatalk/knuth-shuffle.lambdatalk

@@ -0,0 +1,29 @@
+{def shuffle
+
+ {def shuffle.in
+  {lambda {:a}
+   {S.map {{lambda {:a :i}
+                   {A.swap :i
+                           {floor {* {random} {+ :i 1}}}  // j = random integer from 0 to i+1
+                           :a}} :a}
+          {S.serie {- {A.length :a} 1} 0 -1}}}}           // from length-1 to 0
+
+ {lambda {:a}
+  {let { {:b {A.duplicate :a}} }        // optionnaly prevents modifying the original array
+   {S.replace \s by in {shuffle.in :b}  // trim extra spaces
+    :b}}}}                              // return the new array
+-> shuffle
+
+{def A.swap                                    // should probably be promoted as a primitive
+ {lambda {:i :j :a}
+  {let { {:i :i}
+         {:gja {A.get :j :a}}
+         {:b {A.set! :j {A.get :i :a} :a}}
+       } {let { {_ {A.set! :i :gja :b} }}}}}}  // side effect without any return value
+-> A.swap
+
+{def B {A.new a b c d e f g h i j k l m n o p q r s t u v w x y z}}
+-> B
+
+{shuffle {B}}
+-> [z,t,q,w,c,n,a,u,r,y,i,s,f,d,g,m,h,x,b,e,k,p,l,o,j,v]