examples/python/mult.py

   1
   2 print("la multiplication dite russe")
   3
   4 a = int(input("entrez a : "))
   5 b = int(input("entrez b : "))
   6
   7 p = a
   8 q = b
   9
  10 if q < 0:
  11     p = -a
  12     q = -b
  13
  14 #@ assert q >= 0
  15
  16 r = 0
  17 while q > 0:
  18     #@ invariant 0 <= q
  19     #@ invariant r + p * q == a * b
  20     #@ variant   q
  21     print(p, q, r)
  22     if q % 2 == 1:
  23         r += p
  24     p += p
  25     q //= 2
  26 print(p, q, r)
  27 print("a * b =", r)
  28 #@ assert r == a * b