Module frunk::coproduct

Module that holds Coproduct data structures, traits, and implementations

Think of "Coproduct" as ad-hoc enums; allowing you to do something like this

type I32Bool = Coproduct!(i32, bool);
let co1: I32Bool = into_coproduct(3);
let co2: I32Bool = into_coproduct(true);

// Getting stuff
let get_from_1a: Option<&i32> = co1.get();
let get_from_1b: Option<&bool> = co1.get();
assert_eq!(get_from_1a, Some(&3));
assert_eq!(get_from_1b, None);

let get_from_2a: Option<&i32> = co2.get();
let get_from_2b: Option<&bool> = co2.get();
assert_eq!(get_from_2a, None);
assert_eq!(get_from_2b, Some(&true));

Or, if you want to "fold" over all possible values of a coproduct

let folder = hlist![
  |&i| format!("i32 {}", i),
  |&b| String::from(if b { "t" } else { "f" })
];

assert_eq!(co1.as_ref().fold(&folder), "i32 3".to_string());
assert_eq!(co2.as_ref().fold(&folder), "t".to_string());

// There is also a value consuming-variant of fold

let folded = co1.fold(hlist![
  |i| format!("i32 {}", i),
  |b| String::from(if b { "t" } else { "f" })
]);
assert_eq!(folded, "i32 3".to_string());

Enums

CNil	Phantom type for signature purposes only (has no value)
Coproduct	Enum type representing a Coproduct. Think of this as a Result, but capable of supporting any arbitrary number of types instead of just 2.

Traits

CoproductFoldable	Trait for implementing "folding" a Coproduct into a value.
CoproductSelector	Trait for retrieving a coproduct element by type
IntoCoproduct

Functions

into_coproduct

Function for returning a Coproduct from a given type