# class Lambda

#### no package

The `Lambda`

class is a collection of methods to support functional
programming. It is ideally used with `using Lambda`

and then acts as an
extension to Iterable types.

On static platforms, working with the Iterable structure might be slower than performing the operations directly on known types, such as Array and List.

If the first argument to any of the methods is null, the result is unspecified.

See also:

### Static methods

`staticarray<A>(it:Iterable<A>):Array<A>`

Creates an Array from Iterable `it`

.

If `it`

is an Array, this function returns a copy of it.

`staticconcat<T>(a:Iterable<T>, b:Iterable<T>):Array<T>`

Returns a new Array containing all elements of Iterable `a`

followed by
all elements of Iterable `b`

.

If `a`

or `b`

are null, the result is unspecified.

`staticcount<A>(it:Iterable<A>, ?pred:(item:A) ‑> Bool):Int`

Returns the number of elements in `it`

for which `pred`

is true, or the
total number of elements in `it`

if `pred`

is null.

This function traverses all elements.

`staticexists<A>(it:Iterable<A>, f:(item:A) ‑> Bool):Bool`

Tells if `it`

contains an element for which `f`

is true.

This function returns true as soon as an element is found for which a
call to `f`

returns true.

If no such element is found, the result is false.

If `f`

is null, the result is unspecified.

`staticfilter<A>(it:Iterable<A>, f:(item:A) ‑> Bool):Array<A>`

Returns a Array containing those elements of `it`

for which `f`

returned
true.
If `it`

is empty, the result is the empty Array even if `f`

is null.
Otherwise if `f`

is null, the result is unspecified.

`staticfind<T>(it:Iterable<T>, f:(item:T) ‑> Bool):Null<T>`

Returns the first element of `it`

for which `f`

is true.

This function returns as soon as an element is found for which a call to
`f`

returns true.

If no such element is found, the result is null.

If `f`

is null, the result is unspecified.

`staticfindIndex<T>(it:Iterable<T>, f:(item:T) ‑> Bool):Int`

Returns the index of the first element of `it`

for which `f`

is true.

This function returns as soon as an element is found for which a call to
`f`

returns true.

If no such element is found, the result is -1.

If `f`

is null, the result is unspecified.

`staticinlineflatMap<A, B>(it:Iterable<A>, f:(item:A) ‑> Iterable<B>):Array<B>`

A composition of map and flatten.
The order of elements is preserved.
If `f`

is null, the result is unspecified.

`staticinlineflatten<A>(it:Iterable<Iterable<A>>):Array<A>`

Concatenate a list of iterables. The order of elements is preserved.

`staticfold<A, B>(it:Iterable<A>, f:(item:A, result:B) ‑> B, first:B):B`

Functional fold on Iterable `it`

, using function `f`

with start argument
`first`

.

If `it`

has no elements, the result is `first`

.

Otherwise the first element of `it`

is passed to `f`

alongside `first`

.
The result of that call is then passed to `f`

with the next element of
`it`

, and so on until `it`

has no more elements.

If `it`

or `f`

are null, the result is unspecified.

`staticfoldi<A, B>(it:Iterable<A>, f:(item:A, result:B, index:Int) ‑> B, first:B):B`

Similar to fold, but also passes the index of each element to `f`

.

If `it`

or `f`

are null, the result is unspecified.

`staticforeach<A>(it:Iterable<A>, f:(item:A) ‑> Bool):Bool`

Tells if `f`

is true for all elements of `it`

.

This function returns false as soon as an element is found for which a
call to `f`

returns false.

If no such element is found, the result is true.

In particular, this function always returns true if `it`

is empty.

If `f`

is null, the result is unspecified.

`statichas<A>(it:Iterable<A>, elt:A):Bool`

Tells if `it`

contains `elt`

.

This function returns true as soon as an element is found which is equal
to `elt`

according to the `==`

operator.

If no such element is found, the result is false.

`staticindexOf<T>(it:Iterable<T>, v:T):Int`

Returns the index of the first element `v`

within Iterable `it`

.

This function uses operator `==`

to check for equality.

If `v`

does not exist in `it`

, the result is -1.

`staticiter<A>(it:Iterable<A>, f:(item:A) ‑> Void):Void`

Calls `f`

on all elements of `it`

, in order.

If `f`

is null, the result is unspecified.

`staticlist<A>(it:Iterable<A>):List<A>`

Creates a List form Iterable `it`

.

If `it`

is a List, this function returns a copy of it.