Improved eulertotient(n) implementation

imp/math/primes.py

@@ -1,5 +1,10 @@
-from math import gcd
+from math import gcd, inf
-from imp.math.numbers import bigomega
+
+from imp.math.numbers import bigomega, factors
+from imp.extern.primefac import (
+    isprime,
+    primegen as Primes,
+)
 
 def coprime(n: int, m: int) -> bool:
     return gcd(n, m) == 1
@@ -18,68 +23,25 @@ def semiprime(n: int) -> bool:
     '''
     return almostprime(n, 2)
     
-'''
+def eulertotient(x: int | list) -> int:
-Euler's Totient (Phi) Function
+    '''
-'''
+    Evaluates Euler's Totient function.
-def totient(n: int) -> int:
+    Input: `x: int` is prime factorised by Lucas A. Brown's primefac.py
-    phi = int(n > 1 and n)
+           else `x: list` is assumed to the prime factorisation of `x: int`
-    for p in range(2, int(n ** .5) + 1):
+    '''
-        if not n % p:
+    pfactors = x if isinstance(x, list) else factors(n)
-            phi -= phi // p
+    return prod((p-1)*(p**(e-1)) for (p, e) in pfactors)
-            while not n % p:
+# def eulertotient(n: int) -> int:
-                n //= p
+#     '''
-    #if n is > 1 it means it is prime
+#     Uses trial division to compute 
-    if n > 1: phi -= phi // n 
+#     Euler's Totient (Phi) Function.
-    return phi
+#     '''
-
+#     phi = int(n > 1 and n)
-'''
+#     for p in range(2, int(n ** .5) + 1):
-Tests the primality of an integer using its totient.
+#         if not n % p:
-NOTE: If totient(n) has already been calculated 
+#             phi -= phi // p
-      then pass it as the optional phi parameter. 
+#             while not n % p:
-'''
+#                 n //= p
-def is_prime(n: int, phi: int = None) -> bool:
+#     #if n is > 1 it means it is prime
-    return n - 1 == (phi if phi is not None else totient(n))
+#     if n > 1: phi -= phi // n 
-
+#     return phi
-'''
-Prime number generator function.
-Returns the tuple (p, phi(p)) where p is prime
-    and phi is Euler's totient function.
-'''
-def prime_gen(yield_phi: bool = False) -> int | tuple[int, int]:
-    n = 1
-    while True:
-        n += 1
-        phi = totient(n)
-        if is_prime(n, phi=phi):
-            if yield_phi:
-                yield (n, phi)
-            else:
-                yield n
-
-'''
-Returns the prime factorisation of a number.
-Returns a list of tuples (p, m) where p is
-a prime factor and m is its multiplicity.
-NOTE: uses a trial division algorithm
-'''
-def prime_factors(n: int) -> list[tuple[int, int]]:
-    phi = totient(n)
-    if is_prime(n, phi=phi):
-        return [(n, 1)]
-    factors = []
-    for p in prime_gen(yield_phi=False):
-        if p >= n:
-            break
-        # check if divisor
-        multiplicity = 0
-        while n % p == 0:
-            n //= p
-            multiplicity += 1
-        if multiplicity:
-            factors.append((p, multiplicity))
-            if is_prime(n):
-                break
-    if n != 1:
-        factors.append((n, 1))
-    return factors
-            

imp/math/util.py

@@ -1,8 +1,9 @@
+from collections.abc import Iterable
 from itertools import chain, combinations
 
 def digits(n: int) -> int:
     return len(str(n))
 
-def powerset(iterable):
+def powerset(iterable: Iterable) -> Iterable:
     s = list(iterable)
     return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))