# Foldable

`trait Foldable[t: Type -> Type]`

SourceA trait for data structures that can be folded.

### Associated Types

`type Aef: Eff`

SourceThe associated effect of the Foldable which represents the effect of accessing its elements.

### Instances

## Signatures

Left-associative fold of a structure.
Applies `f`

to a start value `s`

and all elements in `t`

going from left to right.

Right-associative fold of a structure.
Applies `f`

to a start value `s`

and all elements in `t`

going from right to left.

`def foldRightWithCont(f: a -> ((Unit -> b \ ef) -> b \ ef), s: b, t: t[a]): b \ ef + Aef[t] with Foldable[t]`

SourceRight-associative fold of a structure.
Applies `f`

to a start value `s`

and all elements in `t`

going from right to left.

A `foldRightWithCont`

allows early termination by not calling the continuation.

## Trait Definitions

Returns the number of elements in `t`

that satisfy the predicate `f`

.

Returns `t`

without the longest prefix that satisfies the predicate `f`

.

Returns an immutable list.

Returns `true`

if and only if at least one element in `t`

satisfies the predicate `f`

.

Returns `false`

if `t`

is empty.

Returns an immutable list of all the elements in `t`

that satisfy the predicate `f`

.

Optionally returns the first element of `t`

that satisfies the predicate `f`

when searching from left to right.

Returns `None`

if `t`

is empty.

Optionally returns the first element of `t`

that satisfies the predicate `f`

when searching from right to left.

Returns `None`

if `t`

is empty.

`def foldLeftM(f: b -> (a -> m[b] \ ef), s: b, t: t[a]): m[b] \ ef + Aef[t] with Foldable[t], Monad[m]`

SourceA monadic version of `foldLeft`

.

Applies the monadic `f`

to a start value `s`

and all elements in `t`

going
from left to right.

Returns the result of mapping each element and combining the results.

`def foldRightM(f: a -> (b -> m[b] \ ef), s: b, t: t[a]): m[b] \ ef + Aef[t] with Foldable[t], Monad[m]`

SourceA monadic version of `foldRight`

.

Applies the monadic `f`

to a start value `s`

and all elements in `t`

going
from right to left.

Returns `true`

if and only if all elements in `t`

satisfy the predicate `f`

.

Returns `true`

if `t`

is empty.

Applies `f`

to each element in `t`

.

A monadic version of `forEach`

.

Apply `f`

to every value in `t`

. `f`

is applied for its monadic effect,
the answer it produces is discarded.

Optionally returns the first element of `t`

.

Returns `None`

if `t`

is empty.

Returns the concatenation of the string representation
of each element in `t`

with `sep`

inserted between each element.

`def joinWith(f: a -> String \ ef, sep: String, t: t[a]): String \ ef + Aef[t] with Foldable[t]`

SourceReturns the concatenation of the string representation
of each element in `t`

according to `f`

with `sep`

inserted between each element.

Optionally returns the last element of `t`

.

Returns `None`

if `t`

is empty.

Optionally finds the largest element of `t`

according to the `Order`

on `a`

.

Returns `None`

if `t`

is empty.

Optionally finds the largest element of `t`

according to the given comparator `cmp`

.

Returns `None`

if `t`

is empty.

Returns `true`

if and only if the element `x`

is in `t`

.

Optionally finds the smallest element of `t`

according to the `Order`

on `a`

.

Returns `None`

if `t`

is empty.

Optionally finds the smallest element of `t`

according to the given comparator `cmp`

.

Returns `None`

if `t`

is empty.

Returns true if and only if `t`

is non-empty.

Optionally applies `f`

to all elements in `t`

going from left to right until a single value is obtained.

Returns `None`

if `t`

is empty.

Optionally applies `f`

to all elements in `t`

going from right to left until a single value is obtained.

Returns `None`

if `t`

is empty.

Returns the sum of all elements in `t`

according to the function `f`

.

Returns the longest prefix of `t`

that satisfies the predicate `f`

.

Returns an immutable list.

Returns `t`

as an array.

Returns `t`

as a `DelayMap`

Returns a map with elements of `s`

as keys and `f`

applied as values.

Returns `t`

as a `MutDeque`

.

Returns `t`

as a mutable list.

`def toMutMap(rc: Region[r], t: t[(k, v)]): MutMap[k, v, r] \ r + Aef[t] with Foldable[t], Order[k]`

SourceReturns `t`

as a `MutMap`

.

Returns the set `s`

as a `MutSet`

.

Optionally returns `t`

as a non empty chain.

Optionally returns `t`

as a non empty list.

## Module Definitions

Returns the result of applying `combine`

to all the elements in `t`

, using `empty`

as the initial value.