Reference · Vectors

vec.mul

vec.mul(list | num, list | num) -> any

What it does

Multiplies item by item: two lists of the same length give a list of their pairwise products, and a list and a number give the list with each item scaled by the number. Ints stay ints and floats stay floats, as with the * operator. Two numbers give their product. For the sum of the products use vec.dot.

Examples

print(vec.mul([1, 2, 3], [4, 5, 6]))print(vec.mul([1, 2, 3], 10))print(vec.mul(0.5, [10, 20]))

[4, 10, 18][10, 20, 30][5.0, 10.0]

Edge cases

• Each pair is typed on its own: [1.5, 2] times 2 is [3.0, 4].
• Scaling by 0 gives zeros, ints for ints and 0.0 for floats.
• The empty list gives the empty list.

print(vec.mul([1.5, 2], 2))print(vec.mul([1, 2.5], 0))print(vec.mul([], 3))

[3.0, 4][0, 0.0][]

Errors

Lists of different lengths, an item that is not an int or a float, or an argument that is neither a list nor a number are runtime errors, not error values. An int product past 64 bits is an integer overflow runtime error; use floats for numbers that large.

print(vec.mul([9223372036854775807], 2))

line 1: integer overflow

print(vec.mul([1, 2], [1]))

line 1: `vec.mul` needs lists of the same length (2 and 1)

Chaining

xs | vec.mul(k) scales a list in a pipeline, often before rounding:

print(vec.linspace(0, 1, 5) | vec.mul(100) | vec.round)print(vec.ones(3) | vec.mul(7))

[0, 25, 50, 75, 100][7, 7, 7]

See also

vec.dot, vec.div, vec.pow, vec.cumprod, math.prod

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