Enum polytype::TypeSchema [−][src]
pub enum TypeSchema<N: Name = &'static str> {
Monotype(Type<N>),
Polytype {
variable: Variable,
body: Box<TypeSchema<N>>,
},
}
Expand description
Represents polytypes (uninstantiated, universally quantified types).
The primary ways of creating a TypeSchema
are with the ptp!
macro or
with Type::generalize
.
Variants
Monotype(Type<N>)
Tuple Fields
0: Type<N>
Non-polymorphic types (e.g. α → β
, int → bool
)
Polytype
Fields
body: Box<TypeSchema<N>>
The type in which variable
is bound
Polymorphic types (e.g. ∀α. α → α
, ∀α. ∀β. α → β
)
Implementations
Parse a TypeSchema
from a string. This round-trips with Display
.
This is a leaky operation and should be avoided wherever possible:
names of constructed types will remain until program termination.
The “for-all” ∀
is optional.
Examples
let t_par = TypeSchema::parse("∀t0. t0 -> t0").expect("valid type");
let t_lit = ptp!(0; @arrow[tp!(0), tp!(0)]);
assert_eq!(t_par, t_lit);
let s = "∀t0. ∀t1. (t1 → t0 → t1) → t1 → list(t0) → t1";
let t: TypeSchema<&'static str> = TypeSchema::parse(s).expect("valid type");
let round_trip = t.to_string();
assert_eq!(s, round_trip);
Checks whether a variable is bound in the quantification of a polytype.
Examples
let t = ptp!(0; @arrow[tp!(0), tp!(1)]); // ∀α. α → β
assert!(t.is_bound(0));
assert!(!t.is_bound(1));
Returns a set of each Variable
bound by the TypeSchema
.
Examples
let t = ptp!(0, 1; @arrow[tp!(1), tp!(2), tp!(3)]); // ∀α. ∀β. β → ɣ → δ
assert_eq!(t.bound_vars(), vec![0, 1]);
Returns a set of each free Variable
in the TypeSchema
.
Examples
let t = ptp!(0, 1; @arrow[tp!(1), tp!(2), tp!(3)]); // ∀α. ∀β. β → ɣ → δ
let mut free = t.free_vars();
free.sort();
assert_eq!(free, vec![2, 3]);
Instantiate a TypeSchema
in the context by removing quantifiers.
All type variables will be replaced with fresh type variables.
Examples
let mut ctx = Context::default();
let t1 = ptp!(3; list(tp!(3)));
let t2 = ptp!(3; list(tp!(3)));
let t1 = t1.instantiate(&mut ctx);
let t2 = t2.instantiate(&mut ctx);
assert_eq!(t1.to_string(), "list(t0)");
assert_eq!(t2.to_string(), "list(t1)");
Like instantiate
, but works in-place.
Trait Implementations
This method tests for self
and other
values to be equal, and is used
by ==
. Read more
This method tests for !=
.
Auto Trait Implementations
impl<N> RefUnwindSafe for TypeSchema<N> where
N: RefUnwindSafe,
impl<N> Send for TypeSchema<N> where
N: Send,
impl<N> Sync for TypeSchema<N> where
N: Sync,
impl<N> Unpin for TypeSchema<N> where
N: Unpin,
impl<N> UnwindSafe for TypeSchema<N> where
N: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
Compare self to key
and return true
if they are equal.