stdlib
stdlib copied to clipboard
gleam-lang
`dict.combine`
It'd be nice to have a Gleam version of this function: https://www.erlang.org/doc/man/maps#merge_with-3
Basically, lets you pass in a function to resolve "merge conflicts", so you could do something like...
let stuff_for_kitchen_to_make: Dict(FoodItem, Int)) =
get_orders_from_every_table() // `List(Dict(FoodItem, Int))`
|> list.fold(dict.new(), fn(a, b) { dict.merge(a, b, int.add) })
My quick implementation looks like...
fn dict_merge_with(
a: Dict(k, v),
b: Dict(k, v),
func: fn(v, v) -> v,
) -> Dict(k, v) {
b
|> dict.to_list()
|> list.fold(a, fn(d, kv) {
dict.update(d, kv.0, fn(count) {
case count {
option.None -> kv.1
option.Some(v) -> func(v, kv.1)
}
})
})
}
...but I have no idea if that's the way you'd like it done. Feel free to copy if you want!
Sounds good, though the name proposed doesn't align with how we normally name functions. What might we call it instead?
Not sure what you mean by “doesn’t align with”.
As some data points tho,
- Elm calls it
merge - Haskell calls it
unionWith - Elixir calls it
merge/3 - Erlang (as mentioned before) calls it
merge_with
Elm and Haskell also both call our current merge union.
optional args would allow to just specify the combiner as an optional arg to our existing merge?
What about calling this one combine, merge_union, union_with or something?
yeah, I think a combine function with a with label for the "merger" function sounds pretty good :)