tasks a-s

Task/Power-set/Icon/power-set-1.icon

@@ -0,0 +1,14 @@
+procedure power_set (s)
+  result := set ()
+  if *s = 0
+    then insert (result, set ()) # empty set
+    else {
+      head := set(?s) # take a random element
+      # and find powerset of remaining part of set
+      tail_pset := power_set (x -- head)
+      result ++:= tail_pset # add powerset of remainder to results
+      every ps := !tail_pset do # and add head to each powerset from the remainder
+        insert (result, ps ++ head)
+    }
+  return result
+end

Task/Power-set/Icon/power-set-2.icon

@@ -0,0 +1,7 @@
+procedure main ()
+  every s := !power_set (set(1,2,3,4)) do { # requires '!' to generate items in the result set
+    writes ("[ ")
+    every writes (!s || " ")
+    write ("]")
+  }
+end

Task/Power-set/Icon/power-set-3.icon

@@ -0,0 +1,19 @@
+procedure power_set (s)
+  if *s = 0
+    then suspend set ()
+    else {
+      head := set(?s)
+      every ps := power_set (s -- head) do {
+        suspend ps
+        suspend ps ++ head
+      }
+    }
+end
+
+procedure main ()
+  every s := power_set (set(1,2,3,4)) do { # power_set's values are generated by 'every'
+    writes ("[ ")
+    every writes (!s || " ")
+    write ("]")
+  }
+end