Data commit

Task/Generator-Exponential/Lua/generator-exponential.lua

@@ -0,0 +1,38 @@
+--could be done with a coroutine, but a simple closure works just as well.
+local function powgen(m)
+  local count = 0
+  return function()
+    count = count + 1
+    return count^m
+  end
+end
+
+local squares = powgen(2)
+local cubes = powgen(3)
+
+local cowrap,coyield = coroutine.wrap, coroutine.yield
+
+local function filter(f,g)
+  return cowrap(function()
+    local ff,gg = f(), g()
+    while true do
+      if ff == gg then
+        ff,gg = f(), g()
+      elseif ff < gg then
+        coyield(ff)
+        ff = f()
+      else
+        gg = g()
+      end
+    end
+  end)
+end
+
+filter = filter(squares,cubes)
+
+for i = 1,30 do
+  local result = filter()
+  if i > 20 then
+    print(result)
+  end
+end