Add Lua port of 03_Animal

03_Animal/lua/Animal.lua

@@ -0,0 +1,181 @@
+--
+-- Animal.lua
+--
+
+-- maintain a flat table/list of all the known animals
+local animals = {
+    "FISH",
+    "BIRD"
+}
+
+-- store the questions as a binary tree with each node having a 
+-- "y" or "n" branch
+-- if the node has a member named "a" it's an answer, with an index
+-- into the animals list.
+-- Otherwise, it's a question that leads to more nodes.
+local questionTree = {
+    q = "DOES IT SWIM",
+    y = { a = 1 },
+    n = { a = 2 }
+}
+
+-- print the given prompt string and then wait for input
+-- loops until a non-empty input is given
+-- returns the input as an upper-case string
+function askPrompt(promptString)
+    local answered = false 
+    local a
+    while (not answered) do 
+        print(promptString)
+        a = io.read()
+        a = string.upper(a)
+        if (string.len(a) > 0) then 
+            answered = true 
+        end
+    end
+    return a
+end
+
+-- print the given prompt string and then wait for the
+-- user to enter a string beginning with "Y" or "N"
+function askYesOrNo(promptString)
+    local a
+    while ((a ~= "Y") and (a ~= "N")) do 
+        a = askPrompt(promptString)
+        a = a:sub(1,1)
+    end
+    return a
+end
+
+-- prints the introductory text from the original BASIC program
+function printIntro()
+    print(string.format("%32s", " ") .. "ANIMAL")
+    print(string.format("%15s", " ") .. "CREATIVE COMPUTING   MORRISTOWN, NEW JERSEY")
+    print()
+    print()
+    print()
+    print("PLAY 'GUESS THE ANIMAL'")
+    print("THINK OF AN ANIMAL AND THE COMPUTER WILL TRY TO GUESS IT.")
+    print()
+end
+
+-- prints the animals known in the source list
+function listKnownAnimals()
+    print()
+    print("ANIMALS I ALREADY KNOW ARE:")
+
+    local x
+    local item
+    for x = 1,#animals do 
+        -- use string.format to space each animal in a 12-character-wide "cell"
+        item = string.format("%-12s", animals[x])
+
+        -- io.write() works like print(), but doesn't automatically add a carriage return/newline
+        io.write(item)
+
+        -- every fifth item, start a new line
+        if ((x % 5) == 0) then 
+            io.write("\n")
+        end
+    end
+
+    print()
+    print()
+end
+
+-- Prompts the user for info about the animal they were thinking of, then
+-- uses that to add a new branch to the tree
+--      curNode: the node in the tree where the computer made a wrong guess
+--      branch: the answer the user gave to curNode's question
+function addAnimalToTree(curNode, branch)
+    local newAnimal 
+    local curResponse = curNode[branch]
+    local guessedIndex = curResponse.a
+    local guessedAnimal = animals[guessedIndex]
+    local newQuestion, newAnswer, newIndex
+    local newNode
+
+    newAnimal = askPrompt("THE ANIMAL YOU WERE THINKING OF WAS A ?")
+    newQuestion = askPrompt("PLEASE TYPE IN A QUESTION THAT WOULD DISTINGUISH A "..
+        tostring(newAnimal).." FROM A "..tostring(guessedAnimal))
+    newAnswer = askYesOrNo("FOR A "..tostring(newAnimal).." THE ANSWER WOULD BE?")
+
+    -- add the new animal to the master list at the end, and
+    -- save off its index in the list
+    table.insert(animals, newAnimal)
+    newIndex = #animals
+
+    -- create a new node for the question we just learned
+    newNode = {}
+    newNode.q = newQuestion
+    if (newAnswer == "Y") then 
+        newNode.y = { a = newIndex }
+        newNode.n = { a = guessedIndex }
+    else 
+        newNode.y = { a = guessedIndex }
+        newNode.n = { a = newIndex }
+    end 
+
+    -- replace the previous answer with our new node
+    curNode[branch] = newNode
+end
+
+-- Starts at the root of the question tree and asks questions about
+-- the user's animal until the computer hits an "a" answer node and tries
+-- to make a guess
+function askAboutAnimal()
+    local curNode = questionTree
+    local finished = false
+    local response, responseIndex
+    local nextNode, animalName
+    while (not finished) do 
+        response = askYesOrNo(curNode.q .. "?")
+        
+        -- convert the response "Y" or "N" to the lowercase "y" or "n" that we use to name our branches
+        branch = string.lower(response)
+        nextNode = curNode[branch]
+        
+        -- is the next node an answer node, or another question?
+        if (nextNode.a ~= nil) then 
+            -- it's an answer, so make a guess
+            animalName = animals[nextNode.a]
+            response = askYesOrNo("IS IT A "..tostring(animalName).."?")
+            if (response == "Y") then
+                -- we got the correct answer, so prompt for a new animal
+                print()
+                print("WHY NOT TRY ANOTHER ANIMAL?")
+            else 
+                -- incorrect answer, so add a new entry at this point in the tree
+                addAnimalToTree(curNode, branch)
+            end
+
+            -- whether we were right or wrong, we're finished with this round
+            finished = true
+        else 
+            -- it's another question, so advance down the tree
+            curNode = nextNode
+        end
+    end
+end
+
+-- MAIN CONTROL SECTION
+
+printIntro()
+
+-- loop forever until the player requests an exit by entering a blank line
+local exitRequested = false
+local answer 
+
+while (not exitRequested) do
+    print("ARE YOU THINKING OF AN ANIMAL?")
+    answer = io.read()
+    answer = string.upper(answer)
+
+    if (string.len(answer) == 0) then
+        exitRequested = true
+    elseif (answer:sub(1,4) == "LIST") then
+        listKnownAnimals()
+    elseif (answer:sub(1,1) == "Y") then
+        askAboutAnimal()
+    end
+end