Built-in types & functions

This page is auto-generated from the prelude source. Run cargo run -p rex --bin gen_prelude_docs to refresh it.

Built-in Types

Type	Description
`Array a`	Fixed-size indexed sequence.
`Dict a`	Dictionary/record-like mapping from field labels to values.
`List a`	Immutable singly linked list. Constructors: `Empty`, `Cons`.
`Option a`	Optional value (`Some` or `None`). Constructors: `Some`, `None`.
`Result a b`	Result value (`Ok` or `Err`) for success/failure flows. Constructors: `Err`, `Ok`.
`bool`	Boolean truth value.
`datetime`	UTC timestamp value.
`f32`	32-bit floating-point number.
`f64`	64-bit floating-point number.
`i16`	16-bit signed integer.
`i32`	32-bit signed integer.
`i64`	64-bit signed integer.
`i8`	8-bit signed integer.
`string`	UTF-8 string value.
`u16`	16-bit unsigned integer.
`u32`	32-bit unsigned integer.
`u64`	64-bit unsigned integer.
`u8`	8-bit unsigned integer.
`uuid`	UUID value.

Built-in Type Classes

`AdditiveGroup`

Types supporting additive inverse and subtraction.

Superclasses: Semiring

Methods:

negate: AdditiveGroup 'a => ('a -> 'a). Additive inverse.
-: AdditiveGroup 'a => ('a -> ('a -> 'a)). Subtraction.

`AdditiveMonoid`

Types with additive identity and associative addition.

Superclasses: none

Methods:

zero: AdditiveMonoid 'a => 'a. Additive identity.
+: AdditiveMonoid 'a => ('a -> ('a -> 'a)). Addition (or concatenation for strings).

`Alternative`

Applicative types with a fallback choice operation.

Superclasses: Applicative

Methods:

or_else: Alternative 'f => ((('f 'a) -> ('f 'a)) -> (('f 'a) -> ('f 'a))). Provide an alternative container value.

`Applicative`

Functors that can lift values and apply wrapped functions.

Superclasses: Functor

Methods:

pure: Applicative 'f => ('a -> ('f 'a)). Lift a plain value into an applicative context.
ap: Applicative 'f => (('f ('a -> 'b)) -> (('f 'a) -> ('f 'b))). Apply wrapped functions to wrapped values.

`Default`

Types with a canonical default value.

Superclasses: none

Methods:

default: Default 'a => 'a. Canonical default value for a type. For Result a e, this requires Default a.

`Eq`

Types supporting equality/inequality comparison.

Superclasses: none

Methods:

==: Eq 'a => ('a -> ('a -> bool)). Equality comparison.
!=: Eq 'a => ('a -> ('a -> bool)). Inequality comparison.

`Field`

Types supporting division in addition to ring operations.

Superclasses: Ring

Methods:

/: Field 'a => ('a -> ('a -> 'a)). Division.

`Filterable`

Functors supporting filtering and partial mapping.

Superclasses: Functor

Methods:

filter: Filterable 'f => (('a -> bool) -> (('f 'a) -> ('f 'a))). Keep elements that satisfy a predicate.
filter_map: Filterable 'f => (('a -> (Option 'b)) -> (('f 'a) -> ('f 'b))). Map and drop missing results in one pass.

`Foldable`

Containers that can be reduced with folds.

Superclasses: none

Methods:

foldl: Foldable 't => (('b -> ('a -> 'b)) -> ('b -> (('t 'a) -> 'b))). Strict left fold.
foldr: Foldable 't => (('a -> ('b -> 'b)) -> ('b -> (('t 'a) -> 'b))). Right fold.
fold: Foldable 't => (('b -> ('a -> 'b)) -> ('b -> (('t 'a) -> 'b))). Left-style fold over a container.

`Functor`

Type constructors that support structure-preserving mapping.

Superclasses: none

Methods:

map: Functor 'f => (('a -> 'b) -> (('f 'a) -> ('f 'b))). Apply a function to each value inside a functor.

`Indexable`

Containers that support indexed element access.

Superclasses: none

Methods:

get: Indexable ('t, 'a) => (i32 -> ('t -> 'a)). Get an element by index.

`Integral`

Integral numeric types supporting modulo.

Superclasses: none

Methods:

%: Integral 'a => ('a -> ('a -> 'a)). Remainder/modulo operation.

`Monad`

Applicatives supporting dependent sequencing (bind).

Superclasses: Applicative

Methods:

bind: Monad 'm => (('a -> ('m 'b)) -> (('m 'a) -> ('m 'b))). Monadic flat-map/sequencing operation.

`MultiplicativeMonoid`

Types with multiplicative identity and associative multiplication.

Superclasses: none

Methods:

one: MultiplicativeMonoid 'a => 'a. Multiplicative identity.
*: MultiplicativeMonoid 'a => ('a -> ('a -> 'a)). Multiplication.

`Ord`

Types with total ordering comparisons.

Superclasses: Eq

Methods:

cmp: Ord 'a => ('a -> ('a -> i32)). Three-way comparison returning negative/zero/positive i32.
<: Ord 'a => ('a -> ('a -> bool)). Less-than comparison.
<=: Ord 'a => ('a -> ('a -> bool)). Less-than-or-equal comparison.
>: Ord 'a => ('a -> ('a -> bool)). Greater-than comparison.
>=: Ord 'a => ('a -> ('a -> bool)). Greater-than-or-equal comparison.

`Ring`

Types supporting additive group plus multiplication.

Superclasses: AdditiveGroup, MultiplicativeMonoid

Methods:

`Semiring`

Types supporting additive and multiplicative monoid operations.

Superclasses: AdditiveMonoid, MultiplicativeMonoid

Methods:

`Sequence`

Ordered containers with slicing/zipping operations.

Superclasses: Functor, Foldable

Methods:

take: Sequence 'f => (i32 -> (('f 'a) -> ('f 'a))). Keep only the first n elements.
skip: Sequence 'f => (i32 -> (('f 'a) -> ('f 'a))). Drop the first n elements.
zip: Sequence 'f => (('f 'a) -> (('f 'b) -> ('f ('a, 'b)))). Pair elements from two containers by position.
unzip: Sequence 'f => (('f ('a, 'b)) -> (('f 'a), ('f 'b))). Split a container of pairs into a pair of containers.

`Show`

Types that can be converted to user-facing strings (Haskell-style naming).

Superclasses: none

Methods:

show: Show 'a => ('a -> string). Render a value as a human-readable string.

Built-in Functions

Overloaded (Type Class Methods)

Function	Signature	Implemented On	Description
`negate`	`('a -> 'a)`	`i8` `i16` `i32` `i64` `f32` `f64`	Additive inverse.
`-`	`('a -> ('a -> 'a))`	`i8` `i16` `i32` `i64` `f32` `f64`	Subtraction.
`zero`	`'a`	`string` `u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64`	Additive identity.
`+`	`('a -> ('a -> 'a))`	`string` `u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64`	Addition (or concatenation for strings).
`or_else`	`((('f 'a) -> ('f 'a)) -> (('f` `'a) -> ('f 'a)))`	`List` `Option` `Array` `(Result 'e)`	Provide an alternative container value.
`pure`	`('a -> ('f 'a))`	`List` `Option` `Array` `(Result 'e)`	Lift a plain value into an applicative context.
`ap`	`(('f ('a -> 'b)) -> (('f 'a)` `-> ('f 'b)))`	`List` `Option` `Array` `(Result 'e)`	Apply wrapped functions to wrapped values.
`default`	`'a`	`bool` `u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string` `(List 'a)` `(Array 'a)` `(Option 'a)` `(Result 'a 'e)`	Canonical default value for a type. For `Result a e`, this requires `Default a`.
`==`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `bool` `string` `uuid` `datetime` `(List 'a)` `(Option 'a)` `(Array 'a)` `(Result 'a 'e)`	Equality comparison.
`!=`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `bool` `string` `uuid` `datetime` `(List 'a)` `(Option 'a)` `(Array 'a)` `(Result 'a 'e)`	Inequality comparison.
`/`	`('a -> ('a -> 'a))`	`f32` `f64`	Division.
`filter`	`(('a -> bool) -> (('f 'a) ->` `('f 'a)))`	`List` `Option` `Array`	Keep elements that satisfy a predicate.
`filter_map`	`(('a -> (Option 'b)) -> (('f` `'a) -> ('f 'b)))`	`List` `Option` `Array`	Map and drop missing results in one pass.
`foldl`	`(('b -> ('a -> 'b)) -> ('b ->` `(('t 'a) -> 'b)))`	`List` `Option` `Array`	Strict left fold.
`foldr`	`(('a -> ('b -> 'b)) -> ('b ->` `(('t 'a) -> 'b)))`	`List` `Option` `Array`	Right fold.
`fold`	`(('b -> ('a -> 'b)) -> ('b ->` `(('t 'a) -> 'b)))`	`List` `Option` `Array`	Left-style fold over a container.
`map`	`(('a -> 'b) -> (('f 'a) -> ('f` `'b)))`	`List` `Option` `Array` `(Result 'e)`	Apply a function to each value inside a functor.
`get`	`(i32 -> ('t -> 'a))`	`((List 'a), 'a)` `((Array 'a), 'a)`	Get an element by index.
`%`	`('a -> ('a -> 'a))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64`	Remainder/modulo operation.
`bind`	`(('a -> ('m 'b)) -> (('m 'a)` `-> ('m 'b)))`	`List` `Option` `Array` `(Result 'e)`	Monadic flat-map/sequencing operation.
`one`	`'a`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64`	Multiplicative identity.
`*`	`('a -> ('a -> 'a))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64`	Multiplication.
`cmp`	`('a -> ('a -> i32))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string`	Three-way comparison returning negative/zero/positive `i32`.
`<`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string`	Less-than comparison.
`<=`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string`	Less-than-or-equal comparison.
`>`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string`	Greater-than comparison.
`>=`	`('a -> ('a -> bool))`	`u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string`	Greater-than-or-equal comparison.
`take`	`(i32 -> (('f 'a) -> ('f 'a)))`	`List` `Array`	Keep only the first `n` elements.
`skip`	`(i32 -> (('f 'a) -> ('f 'a)))`	`List` `Array`	Drop the first `n` elements.
`zip`	`(('f 'a) -> (('f 'b) -> ('f` `('a, 'b))))`	`List` `Array`	Pair elements from two containers by position.
`unzip`	`(('f ('a, 'b)) -> (('f 'a),` `('f 'b)))`	`List` `Array`	Split a container of pairs into a pair of containers.
`show`	`('a -> string)`	`bool` `u8` `u16` `u32` `u64` `i8` `i16` `i32` `i64` `f32` `f64` `string` `uuid` `datetime` `(List 'a)` `(Array 'a)` `(Option 'a)` `(Result 'a 'e)`	Render a value as a human-readable string.

Other Built-ins

Function	Signature	Description
`&&`	`(bool -> (bool -> bool))`	Boolean conjunction.
`Cons`	`('a -> ((List 'a) -> (List` `'a)))`	Construct a non-empty list from head and tail.
`Empty`	`(List 'a)`	The empty list constructor.
`Err`	`('e -> (Result 't 'e))`	Construct a failed `Result`.
`None`	`(Option 't)`	The empty `Option` constructor.
`Ok`	`('t -> (Result 't 'e))`	Construct a successful `Result`.
`Some`	`('t -> (Option 't))`	Construct a present `Option` value.
`count`	`Foldable 'f => (('f 'a) ->` `i32)`	Count elements in a foldable container.
`is_err`	`((Result 't 'e) -> bool)`	Check whether a `Result` is `Err`.
`is_none`	`((Option 'a) -> bool)`	Check whether an `Option` is `None`.
`is_ok`	`((Result 't 'e) -> bool)`	Check whether a `Result` is `Ok`.
`is_some`	`((Option 'a) -> bool)`	Check whether an `Option` is `Some`.
`max`	`Foldable 'f, Ord 'a => (('f` `'a) -> 'a)`	Maximum element by ordering.
`mean`	`Foldable 'f, Field 'a => (('f` `'a) -> 'a)`	Arithmetic mean over numeric foldables.
`min`	`Foldable 'f, Ord 'a => (('f` `'a) -> 'a)`	Minimum element by ordering.
`sum`	`Foldable 'f, AdditiveMonoid 'a` `=> (('f 'a) -> 'a)`	Sum all elements in a foldable container.
`to_array`	`((List 'a) -> (Array 'a))`	Convert a list to an array.
`to_list`	`((Array 'a) -> (List 'a))`	Convert an array to a list.
`		`

Keyboard shortcuts

Rex