use while to implement randomize (thanks joe!), document it

basis/random/random-docs.factor

@@ -57,6 +57,13 @@ HELP: with-system-random
 
 { with-random with-secure-random with-system-random } related-words
 
+HELP: randomize
+{ $values
+     { "seq" sequence }
+     { "seq" sequence }
+}
+{ $description "Randomizes a sequence in-place with the Fisher-Yates algorithm and returns the sequence." } ;
+
 HELP: delete-random
 { $values
      { "seq" sequence }
@@ -83,6 +90,8 @@ $nl
 { $subsection with-secure-random }
 "Implementation:"
 { $subsection "random-protocol" }
+"Randomizing a sequence:"
+{ $subsection randomize }
 "Deleting a random element from a sequence:"
 { $subsection delete-random } ;
 

basis/random/random-tests.factor

@@ -18,14 +18,8 @@ IN: random.tests
 
 [ f ] [ 0 random ] unit-test
 
-[ 0 ] [ { } >randomize-range length ] unit-test
-[ 0 ] [ { 1 } >randomize-range length ] unit-test
-
 [ { } ] [ { } randomize ] unit-test
 [ { 1 } ] [ { 1 } randomize ] unit-test
 
 [ f ]
 [ 100 [ { 0 1 } random ] replicate all-equal? ] unit-test
-
-[ t ]
-[ { 1 2 } [ length ] [ >randomize-range length ] bi - 1 = ] unit-test

basis/random/random.factor

@@ -43,9 +43,6 @@ M: f random-32* ( obj -- * ) no-random-number-generator ;
     [ random-bytes >byte-array byte-array>bignum ]
     [ 3 shift 2^ ] bi / * >integer ;
 
-: >randomize-range ( seq -- range/iota )
-    length dup 2 < [ drop 0 iota ] [ 1+ 2 (a,b] ] if ;
-
 PRIVATE>
 
 : random-bits ( n -- r ) 2^ random-integer ;
@@ -55,9 +52,10 @@ PRIVATE>
         [ length random-integer ] keep nth
     ] if-empty ;
 
-: randomize ( seq -- seq' )
+: randomize ( seq -- seq )
-    [ ] [ >randomize-range ] [ ] tri
+    dup length [ dup 1 > ]
-    '[ [ random ] [ 1- ] bi _ exchange ] each ;
+    [ [ random ] [ 1- ] bi [ pick exchange ] keep ]
+    [ ] while drop ;
 
 : delete-random ( seq -- elt )
     [ length random-integer ] keep [ nth ] 2keep delete-nth ;