Reference · Vectors

vec.cumprod

vec.cumprod(list | null) -> list

What it does

The running product: a list where each item is the product of the input up to and including that position. Ints stay ints and floats stay floats, as with *.

Examples

print(vec.cumprod([1, 2, 3, 4]))print(vec.cumprod([2, 0.5, 4]))

[1, 2, 6, 24][2, 1.0, 4.0]

Edge cases

• The empty list, or null, gives the empty list; one item gives itself.
• A zero makes every later item zero.
• Growth factors chained this way give the compounded value at each step.

print(vec.cumprod([]), vec.cumprod(null), vec.cumprod([3]))print(vec.cumprod([1, 0, 5]))print(vec.cumprod([1.1, 1.1, 1.1]) | vec.round(3))

[] [] [3][1, 0, 0][1.1, 1.21, 1.331]

Errors

An item that is not an int or a float, or an argument that is not a list, is a runtime error, not an error value. An int product past 64 bits is an integer overflow runtime error; use floats when the products grow that large.

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

line 1: integer overflow

print(vec.cumprod(["a"]))

line 1: `vec.cumprod` expects numbers, got str

Chaining

print(vec.arange(1, 6) | vec.cumprod)print(vec.full(3, 2) | vec.cumprod | last)

[1, 2, 6, 24, 120]8

See also

vec.cumsum, vec.mul, math.prod

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