Add tests and planning doc

numberwords.py

@@ -1,88 +1,59 @@
-# int_to_text.py
+# numberwords.py
 # --------------
+# By MWC Contributors
 # Functions to print out a verbal representation of an integer.
 
 MAXIMUM = 1000000
+DIGIT_NAMES = [
+    "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"
+]
+TWEEN_AND_TEEN_NAMES = [
+    "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"
+]
+TENS_NAMES = [
+    "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"
+]
 
-def int_under_1000000_to_text(number):
+def int_under_1000000_to_str(number):
     "Returns a textual representation of the number."
-    check_number_in_range(abs(number), 1 , MAXIMUM)
+    check_number_in_range(abs(number), 0, MAXIMUM)
     if number < 1000:
-        return int_under_1000_to_text(number)
+        return int_under_1000_to_str(number)
     else:
         thousands, hundreds = divide_with_remainder(number, 1000)
-        thousands_text = int_under_1000_to_text(thousands)
-        hundreds_text = int_under_1000_to_text(hundreds)
+        thousands_text = int_under_1000_to_str(thousands)
+        hundreds_text = int_under_1000_to_str(hundreds)
         return thousands_text + " thousand " + hundreds_text
         
-def int_under_1000_to_text(number):
+def int_under_1000_to_str(number):
     "Returns a textual representation of the number"
-    check_number_in_range(number, 1, 1000)
+    check_number_in_range(number, 0, 1000)
     if number < 100:
-        return int_under_100_to_text(number)
+        return int_under_100_to_str(number)
     else:
         hundreds, tens = divide_with_remainder(number, 100)
-        hundreds_text = int_under_10_to_text(hundreds)
-        tens_text = int_under_100_to_text(tens)
+        hundreds_text = int_under_10_to_str(hundreds)
+        tens_text = int_under_100_to_str(tens)
         return hundreds_text + " hundred and " + tens_text
 
-def int_under_100_to_text(number):
-    check_number_in_range(number, 1, 100)
-    if number < 10:
-        return int_under_10_to_text(number)
+def int_under_100_to_str(number):
+    check_number_in_range(number, 0, 100)
+    tens, ones = divide_with_remainder(number, 10)
+    if tens == 0:
+        return int_under_10_to_str(number)
+    elif tens == 1:
+        return TWEEN_AND_TEEN_NAMES[ones]
     else:
-        tens, ones = divide_with_remainder(number, 10)
-        if tens == 9: 
-            return "ninety-" + int_under_10_to_text(ones)
-        elif tens == 8:
-            return "eighty-" + int_under_10_to_text(ones)
-        elif tens == 7:
-            return "seventy-" + int_under_10_to_text(ones)
-        elif tens == 6:
-            return "sixty-" + int_under_10_to_text(ones)
-        elif tens == 5:
-            return "fifty-" + int_under_10_to_text(ones)
-        elif tens == 4:
-            return "forty-" + int_under_10_to_text(ones)
-        elif tens == 3:
-            return "thirty-" + int_under_10_to_text(ones)
-        elif tens == 2:
-            return "twenty-" + int_under_10_to_text(ones)
-        elif number >= 16:
-            return int_under_10_to_text(ones) + "teen"
-        elif number == 15:
-            return "fifteen"
-        elif number == 14:
-            return "fourteen"
-        elif number == 13:
-            return "thirteen"
-        elif number == 12:
-            return "twelve"
-        elif number == 11:
-            return "eleven"
+        return TENS_NAMES[tens] + '-' + int_under_10_to_str(ones)
 
-def int_under_10_to_text(number):
-    check_number_in_range(number, 1, 10)
-    if number == 1:
-        return "one"
-    elif number == 2:
-        return "two"
-    elif number == 3:
-        return "three"
-    elif number == 4:
-        return "four"
-    elif number == 5:
-        return "five"
-    elif number == 6:
-        return "six"
-    elif number == 7:
-        return "seven"
-    elif number == 8:
-        return "eight"
-    elif number == 9:
-        return "nine"
+def int_under_10_to_str(number):
+    check_number_in_range(number, 0, 10)
+    return DIGIT_NAMES[number]
 
 def check_number_in_range(number, minimum, maximum):
+    """Checks whether a number is at least minimum and less than maximum. 
+    Raises an error if the number is not in range.
+    """
     if number < minimum:
         raise ValueError(f"{number} must not be below {minimum}.")
     if number >= maximum: