added animal guessing game example

docs/source/todo.rst

@@ -2,6 +2,8 @@
 TODO
 ====
 
+- alllow uword xx=memory()  initialization in block scope.
+
 - hoist all variable declarations up to the subroutine scope *before* even the constant folding takes place (to avoid undefined symbol errors when referring to a variable from another nested scope in the subroutine)
 - optimize swap of two memread values with index, using the same pointer expression/variable, like swap(@(ptr+1), @(ptr+2))
 - optimize several inner loops in gfx2 (highres 4 color mode)

examples/animals.p8

@@ -0,0 +1,144 @@
+%import textio
+%import string
+
+; Animal guessing game where the computer gets smarter every time.
+; Note: this program is compatible with C64 and CX16.
+
+
+main {
+    const ubyte database_size = 100
+
+    uword animal_names_buf
+    uword questions_buf
+    uword animal_names_ptr
+    uword questions_ptr
+
+    uword[database_size] animals
+    uword[database_size] questions
+    uword[database_size] answers_questions
+    uword[database_size] answers_animals
+    ubyte new_animal_number
+    ubyte new_question_number
+    str userinput = "x"*80
+
+    sub start() {
+        ; initialize the database
+        animal_names_buf = memory("animalnames", 500)
+        questions_buf = memory("questions", 2000)
+        animal_names_ptr = animal_names_buf
+        questions_ptr = questions_buf
+
+        animals[0] = 0
+        animals[1] = "dolphin"
+        animals[2] = "eagle"
+        animals[3] = "horse"
+        new_animal_number = 4
+
+        questions[0] = 0
+        questions[1] = "does it swim"
+        questions[2] = "can it fly"
+        new_question_number = 3
+
+        answers_questions[0] = mkword(0, 0)
+        answers_questions[1] = mkword(0, 2)
+        answers_questions[2] = mkword(0, 0)
+
+        answers_animals[0] = mkword(0, 0)
+        answers_animals[1] = mkword(1, 0)
+        answers_animals[2] = mkword(2, 3)
+
+        ; play the game
+        game()
+    }
+
+    sub game() {
+        repeat {
+            ubyte current_question = 1
+            txt.print("\n\nanimal guessing game!\nthink of an animal.\n")
+            ubyte guessed = false
+            while not guessed {
+                txt.print(questions[current_question])
+                txt.print("? ")
+                if txt.input_chars(userinput) {
+                    txt.nl()
+                    ubyte animal_number
+                    if userinput[0]=='y' {
+                        animal_number = msb(answers_animals[current_question])
+                        if animal_number {
+                            guess(current_question, true, animal_number)
+                            guessed = true
+                        } else {
+                            current_question = msb(answers_questions[current_question])
+                        }
+                    }
+                    else if userinput[0]=='n' {
+                        animal_number = lsb(answers_animals[current_question])
+                        if animal_number {
+                            guess(current_question, false, animal_number)
+                            guessed = true
+                        } else {
+                            current_question = lsb(answers_questions[current_question])
+                        }
+                    }
+                    else {
+                        txt.print("answer (y)es or (n)o please.\n")
+                    }
+                } else
+                    txt.nl()
+            }
+        }
+    }
+
+    sub guess(ubyte question_number, ubyte given_answer_yesno, ubyte animal_number) {
+        txt.print("is it a ")
+        txt.print(animals[animal_number])
+        txt.print("? ")
+        txt.input_chars(userinput)
+        if userinput[0] == 'y' {
+            txt.print("\n\nsee, i knew it!\n")
+            return
+        }
+
+        str name = "x"*30
+        txt.print("\n\ni give up. what is it? ")
+        txt.input_chars(name)
+        txt.print("\nwhat yes-no question would best articulate the difference\nbetween a ")
+        txt.print(animals[animal_number])
+        txt.print(" and a ")
+        txt.print(name)
+        txt.print("? ")
+        txt.input_chars(userinput)
+        txt.print("\nfor a ")
+        txt.print(name)
+        txt.print(", what is the answer to that; yes or no? ")
+        str answer = "x"*10
+        txt.input_chars(answer)
+
+        animals[new_animal_number] = animal_names_ptr
+        questions[new_question_number] = questions_ptr
+        animal_names_ptr += string.copy(name, animal_names_ptr)+1  ; store animal name in buffer
+        questions_ptr += string.copy(userinput, questions_ptr)+1   ; store question in buffer
+
+        answers_questions[new_question_number] = mkword(0, 0)
+        if answer[0]=='y'
+            answers_animals[new_question_number] = mkword(new_animal_number, animal_number)
+        else
+            answers_animals[new_question_number] = mkword(animal_number, new_animal_number)
+
+        uword previous_animals = answers_animals[question_number]
+        uword previous_questions = answers_questions[question_number]
+        if given_answer_yesno {
+            answers_animals[question_number] = mkword(0, lsb(previous_animals))
+            answers_questions[question_number] = mkword(new_question_number, lsb(previous_questions))
+        } else {
+            answers_animals[question_number] = mkword(msb(previous_animals), 0)
+            answers_questions[question_number] = mkword(msb(previous_questions), new_question_number)
+        }
+
+        new_animal_number++
+        new_question_number++
+
+        txt.print("\n\nthanks, i know more animals now! let's try again.\n")
+
+    }
+}