carmichael_number - add doctests

maths/carmichael_number.py

@@ -11,16 +11,20 @@
 https://en.wikipedia.org/wiki/Carmichael_number
 """
 
-
-def gcd(a: int, b: int) -> int:
-    if a < b:
-        return gcd(b, a)
-    if a % b == 0:
-        return b
-    return gcd(b, a % b)
+from maths.greatest_common_divisor import greatest_common_divisor
 
 
 def power(x: int, y: int, mod: int) -> int:
+    """
+
+    Examples:
+    >>> power(2, 15, 3)
+    2
+
+    >>> power(5, 1, 30)
+    5
+    """
+
     if y == 0:
         return 1
     temp = power(x, y // 2, mod) % mod
@@ -31,15 +35,46 @@ def power(x: int, y: int, mod: int) -> int:
 
 
 def is_carmichael_number(n: int) -> bool:
-    b = 2
-    while b < n:
-        if gcd(b, n) == 1 and power(b, n - 1, n) != 1:
-            return False
-        b += 1
-    return True
+    """
+
+    Examples:
+    >>> is_carmichael_number(562)
+    False
+
+    >>> is_carmichael_number(561)
+    True
+
+    >>> is_carmichael_number(5.1)
+    Traceback (most recent call last):
+         ...
+    ValueError: Number 5.1 must instead be integer
+
+    >>> is_carmichael_number(-7)
+    Traceback (most recent call last):
+         ...
+    ValueError: Number -7 must instead be integer
+
+    >>> is_carmichael_number(0)
+    Traceback (most recent call last):
+         ...
+    ValueError: Number 0 must instead be integer
+    """
+
+    if n <= 0 or not isinstance(n, int):
+        msg = f"Number {n} must instead be integer"
+        raise ValueError(msg)
+
+    return all(
+        power(b, n - 1, n) == 1
+        for b in range(2, n) if greatest_common_divisor(b, n) == 1
+    )
 
 
 if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+
     number = int(input("Enter number: ").strip())
     if is_carmichael_number(number):
         print(f"{number} is a Carmichael Number.")