Higher-order functions: Difference between revisions

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 First define the higher order functions <code>fold</code>, <code>map</code>, and <code>filter</code>.
-<pre>  [ stack ]                     is fold.act (     --> s )
+<pre>  [ over [] = iff drop done
+     dip
-  protect fold.act
+       [ behead swap
+        ' [ witheach ] ]
-  [ fold.act put
+     nested join do ]       is fold   ( [ x --> x )
-    [ dup [] = if done
-      behead swap
-      witheach
-        [ fold.act share do ] ]
-    fold.act release ]          is fold     ( [ x --> x )
   [ ' [ [ ] ] rot join swap
     nested
     ' [ nested join ] join
-    fold ]                      is map      ( [ x --> [ )
+    fold ]                  is map    ( [ x --> [ )
   [ ' [ [ ] ] rot join swap
@@ Line 3,544: / Line 3,540: @@
     ' [ iff [ nested join ]
         else drop ] join
-    fold ]                      is filter   ( [ x --> [ )
+    fold ]                  is filter ( [ x --> [ )
 </pre>