Std.Map.upsert
1 declaration
fn
upsert: &Map[K, V] -> K -> V -> fn(V) -> V -> Map[K, V]This is a callable function.
What it does
An entry's value transformed, inserting a starting value when it is absent.
This is how a counter or an accumulator is kept in a map without the caller
writing the same two-case match every time.
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.