Project is now named Celeste

celeste/math/primes/__init__.py

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+from math import inf, isqrt # integer square root
+from itertools import takewhile, compress
+
+SMALL_PRIMES = (2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59)
+
+'''
+Euler's Totient (Phi) Function 
+Implemented in O(nloglog(n)) using the Sieve of Eratosthenes.
+'''
+def eulertotient(n: int) -> int:
+    phi = int(n > 1 and n)
+    for p in range(2, isqrt(n) + 1):
+        if not n % p:
+            phi -= phi // p
+            while not n % p:
+                n //= p
+    #if n is > 1 it means it is prime
+    if n > 1: phi -= phi // n 
+    return phi
+
+'''
+Tests the primality of an integer using its totient.
+NOTE: If totient(n) has already been calculated 
+      then pass it as the optional phi parameter. 
+'''
+def is_prime(n: int, phi: int = None) -> bool:
+    return n - 1 == (phi if phi is not None else eulertotient(n))
+
+# Taken from Lucas A. Brown's primefac.py (some variables renamed)
+def primegen(limit=inf) -> int:
+    ltlim = lambda x: x < limit
+    yield from takewhile(ltlim, SMALL_PRIMES)
+    pl, prime = [3,5,7], primegen()
+    for p in pl: next(prime)
+    n = next(prime); nn = n*n
+    while True:
+        n = next(prime); ll, nn = nn, n*n
+        delta = nn - ll
+        sieve = bytearray([True]) * delta
+        for p in pl:
+            k = (-ll) % p
+            sieve[k::p] = bytearray([False]) * ((delta-k)//p + 1)
+        if nn > limit: break
+        yield from compress(range(ll,ll+delta,2), sieve[::2])
+        pl.append(n)
+    yield from takewhile(ltlim, compress(range(ll,ll+delta,2), sieve[::2]))
+
+