Improved handling of prime factors, proper divisors, and aliquots

imp/math/numbers.py

@@ -1,16 +0,0 @@
-from imp.math.primefac import factors
-
-def divisors(n: int) -> int:
-    '''
-    Returns the proper divisors of an integer n.
-    Also called the "aliquot parts" of n. 
-    '''
-    pf = factors(n)
-    for (prime, multiplicity) in pf:
-    
-
-def aliquots(n: int) -> int:
-    return proper_divisors(n)
-
-def amicable(n: int) -> int:
-    sum(proper_divisors())

imp/math/numbers/__init__.py

@@ -0,0 +1,82 @@
+'''
+Terminology:
+    Although "divisor" and "factor" mean the same thing.
+    When Celeste discusses "divisors of n" it is implied to
+    mean "proper divisors of n + n itself", and "factors" are
+    the "prime proper divisors of n". 
+'''
+
+from imp.math.primefac import primefac
+
+def factors(n: int) -> int:
+    pfactors: list[tuple[int, int]] = []
+    # generate primes and progressively store them in pfactors
+    pfgen = primefac(n)
+    watching = next(pfgen)
+    mult = 1
+    # ASSUMPTION: prime generation is (non-strict) monotone increasing
+    while True:
+        p = next(pfgen, None)
+        if p == watching:
+            mult += 1
+        else:
+            pfactors.append((watching, mult))
+            watching = p # reset
+            mult = 1     # reset 
+        if p is None: 
+            break
+    return pfactors
+
+def factors2divisors(pfactors: list[tuple[int, int]], 
+                     sorted: bool = True) -> list[int]:
+    '''
+    Generates all divisors < n of an integer n given its prime factorisation.
+    Input: prime factorisation of n (excluding 1 and n, and duplicates)
+           in the typical form: list[(prime, multiplicity)]
+    ''' 
+    divisors = [1]
+    for (prime, multiplicity) in pfactors:
+        extension = []
+        for i in range(1, multiplicity+1):
+            term = prime**i
+            extension.extend(list([divisor*term for divisor in divisors]))
+        divisors.extend(extension)
+    if sorted: divisors.sort()
+    return divisors
+
+def factors2aliquots(pfactors: list[tuple[int, int]]) -> list[int]:
+    return factors2divisors(pfactors)[:-1]
+    
+# "aliquots(n)" is an alias for "divisors(n)"
+def aliquots(n: int) -> int:
+    '''
+    Returns all aliquot parts (proper divisors) of
+    an integer n, that is all divisors 0 < d <= n. 
+    '''
+    return factors2aliquots(factors(n))
+
+def divisors(n: int) -> int:
+    '''
+    Returns all divisors 0 < d < n of an integer n.
+    '''
+    return factors2divisors(factors(n))
+
+def aliquot_sum(n: int) -> int:
+    return sum(aliquots(n))
+
+
+def littleomega(n: int) -> int:
+    '''
+    The Little Omega function counts the number of 
+    distinct prime factors of an integer n.
+    Ref: https://en.wikipedia.org/wiki/Prime_omega_function
+    '''
+    return len(factors(n))
+
+def bigomega(n: int) -> int:
+    '''
+    The Big Omega function counts the total number of
+    prime factors (including multiplicity) of an integer n. 
+    Ref: https://en.wikipedia.org/wiki/Prime_omega_function
+    '''
+    return sum(factor[1] for factor in factors(n))