Reference · Lists

zip

zip(list | null, list | null) -> list

What it does

Pairs the two lists item by item: a list of [a, b] lists, the first of each, then the second, and so on, as long as the shorter list. null counts as an empty list.

Examples

print(zip([1, 2, 3], ["a", "b", "c"]))let names = ["ann", "bob"]let ages = [30, 40]for [name, age] in zip(names, ages) {    print(name, age)}print(zip(names, ages) | map((p) => { name: p[0], age: p[1] }))

[[1, "a"], [2, "b"], [3, "c"]]ann 30bob 40[{ name: "ann", age: 30 }, { name: "bob", age: 40 }]

Edge cases

• The result is as long as the shorter list; the extra items of the longer one are dropped without an error.
• Either list empty or null gives [].
• Each pair is a two-item list: p[0], p[1], or let [a, b] = p.
• Pairing a list with its indexes is enumerate.

print(zip([1, 2, 3], ["a"]), zip([], [1]), zip(null, [1]), zip([1], null))print(zip(["a", "b"], range(2)), enumerate(["a", "b"]))

[[1, "a"]] [] [] [][["a", 0], ["b", 1]] [[0, "a"], [1, "b"]]

Errors

An argument that is not a list or null is a runtime error, not an error value.

print(zip([1], "ab"))

line 1: `zip` expects a list as argument 2, got str

Chaining

In a pipeline the first list comes first and the second is the only argument: xs | zip(ys). The pairs go on to a map that combines them.

print([1, 2, 3] | zip([10, 20, 30]) | map((p) => p[0] + p[1]))print(["x", "y"] | zip([1, 2]) | map((p) => `${p[0]}=${p[1]}`) | join("&"))

[11, 22, 33]x=1&y=2

See also

enumerate, map, flatten, range

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