Std.Map.alter
1 declaration
fn
alter: &Map[K, V] -> K -> fn(Option[V]) -> Option[V] -> Map[K, V]This is a callable function.
What it does
An entry inserted, replaced, or removed by one transformation.
The general form the others are special cases of: None in means the key is
absent, and None out removes it.
Read the signature
- The text after the name is the type checked by Pudu.
- Read arrows from left to right: inputs come first, and the final type is returned.
- & borrows a value for this call instead of moving or copying it.
- Names inside [ ] are type arguments, such as the item type held by a collection.
- Option holds Some(value) or None when no value is available.