indexof

Builtin index · Collections & strings

result = indexof(collection, value)

Input: collection, value · Output: result

What it is

collection is a Vec or List; value is any comparable element.

Overloads

One call shape — this function is not overloaded.

Code	Input	Output	Description
`result = indexof(collection, value)`	`collection` Vec or List`collection` is a `Vec` or `List`. `value` —`value` is any comparable element.	`number` —0-based index of the first match	Returns a `number` (0-based index of the first match) or `Nothing` if absent (composes with `??`: `indexof(xs, v) ?? -1`).

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

ys = [3, 1, 4, 1, 5]
print(contains(ys, 4))     # true

print(indexof(ys, 4))      # 2

print(cumsum(ys))          # [3, 4, 8, 9, 14]

print(numel(ys))           # 5

output

true
2
[3, 4, 8, 9, 14]
5

from collections-strings

How it works

indexof(collection, value) — index of the first element equal to value, or Value::Nothing if absent. Nothing (not -1) is Qu's existing "absent" marker (see how ??/ Expr::Coalesce already treats it specially) — composes directly with that operator: indexof(xs, v) ?? -1 for scripts that do want a sentinel index. index_of is accepted as well: it is the spelling most people reach for, and having only one of the two is a guessing game with no payoff.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.