The way you usually convert a &str to a String is to_owned, e.g. “me”.to_owned() However, you can’t do pattern matching on a String. You could expect a success, get a &str from the String then pattern match on that: fn player_starts() -> bool { println!(“Who will start (me/you)”); loop { let input = readline::readline(“>”); match … Read more
Axiom K is also called the principle of uniqueness of identity proofs, and it is an axiom about the nature of the identity type in Martin-Löf’s dependent type theory. This type doesn’t exist (and in fact cannot be defined) in simpler type theories such as System F, so that is probably the reason why you … Read more
Quick Solution You just need to add parentheses, or begin/end, around the inner match: let rec filter exp = match exp with | Var v -> Var v | Sum (e1, e2) -> Sum (e1, e2) | Prod (e1, e2) -> Prod (e1, e2) | Diff (e1, e2) -> (match e2 with | Sum (e3, … Read more
It works this way by design, but admittedly it can be a bit confusing at first glance. This feature allows you to destructure maps using pattern matching, without having to specify all keys. For example: iex> %{b: value} = %{a: 1, b: 2, c: 3} %{a: 1, b: 2, c: 3} iex> value 2 Consequently, … Read more