Update itertools recipe to reflect the promotion.

Author: rhettinger

Doc/library/itertools.rst

@@ -33,7 +33,7 @@ by combining :func:`map` and :func:`count` to form ``map(f, count())``.
 These tools and their built-in counterparts also work well with the high-speed
 functions in the :mod:`operator` module.  For example, the multiplication
 operator can be mapped across two vectors to form an efficient dot-product:
-``sum(map(operator.mul, vector1, vector2))``.
+``sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))``.
 
 
 **Infinite iterators:**
@@ -838,10 +838,6 @@ which incur interpreter overhead.
        "Returns the sequence elements n times"
        return chain.from_iterable(repeat(tuple(iterable), n))
 
-   def dotproduct(vec1, vec2):
-       "Compute a sum of products."
-       return sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))
-
    def convolve(signal, kernel):
        # See:  https://betterexplained.com/articles/intuitive-convolution/
        # convolve(data, [0.25, 0.25, 0.25, 0.25]) --> Moving average (blur)
@@ -852,7 +848,7 @@ which incur interpreter overhead.
        window = collections.deque([0], maxlen=n) * n
        for x in chain(signal, repeat(0, n-1)):
            window.append(x)
-           yield dotproduct(kernel, window)
+           yield math.sumprod(kernel, window)
 
    def polynomial_from_roots(roots):
        """Compute a polynomial's coefficients from its roots.