Created modules.lua, added functions to it

Modules/modules.lua

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+--[[Function Module program by Al Sweigart
+Provides useful utility functions.]]
+
+-- selectItem() selects the inventory
+-- slot with the named item, returns
+-- true if found and false if not
+function selectItem(name)
+-- check all inventory slots
+ local item
+  for slot = 1, 16 do
+    item = turtle.getItemDetail(slot)
+    if item ~= nil and item['name'] == name then
+      turtle.select(slot)
+      return true
+    end
+  end
+
+  return false  -- couldn't find item
+end
+
+
+-- selectEmptySlot() selects inventory
+-- slot that is empty, returns true if
+-- found, false if no empty spaces
+function selectEmptySlot()
+
+  -- loop through all slots
+  for slot = 1, 16 do  
+    if turtle.getItemCount(slot) == 0 then
+      turtle.select(slot)
+      return true
+    end
+  end
+  return false -- couldn't find empty space
+end
+
+-- countInventory() returns the total
+-- numer of items in the inventory
+function countInventory()
+    local total = 0
+
+    for slot = 1, 16 do
+        total = total + turtle.getItem(slot)
+    end
+    return total
+end
+
+-- selectAndPlaceDown() selects a nonempty slot
+-- and places a block from it under the turtle
+function selectAndPlaceDown()
+    for slot = 1, 16 do
+        if turtle.getItemCount(slot) > 0 then
+            turtle.select(slot)
+            turtle.placeDown()
+            return
+        end
+    end
+end
+
+
+-- buildWall() creates a wall stretching
+-- in front of the turtle
+function buildWall(length, height)
+    if modules.countInventory() > length * height then
+        return false --not enough block
+    end
+
+    turtle.up()
+
+    local movingForward = true
+
+    for currentHeight = 1, height do
+        for currentLength = 1, length do
+            selectAndPlaceDown() -- Place the block
+            if movingForward and currentLength ~= length then
+                turtle.forward()
+            elseif not movingForward and currentLength ~= length then
+                turtle.back()
+            end
+        end
+        if currentHeight ~= height then
+            turtle.up()
+        end
+        movingForward = not movingForward
+    end
+
+    -- done building wall; move to end position
+    if movingForward then
+        -- turtle is near the start position
+        for currentLength = 1, length do
+            turtle.forward()
+        end
+    else
+        -- turtle is near the end position
+        turtle.forward()
+    end
+
+    -- move down to the ground
+    for currentHeight = 1, height do
+        turtle.down()
+    end
+
+    return true
+end