classDocs / Stack

Stack

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Object → Stack

A stack is a last-in-first-out (LIFO) data structure object.

Values are added and removed from the same end (the "top") via push and pop, so the most recently pushed value is always the first one popped.

The stack can also be iterated destructively with iterator, which pops values one by one until it is empty.

Constructor

Stack(): Stack

Fields

Name	Type	Description
`size`	`integer`	The size of the stack. Read-only

Methods

`clear`	Empties the stack, removing every value and resetting its size to 0.
`filter`	Removes every item for which predicate returns true, keeping the order of the remaining items.
`isEmpty`	Checks if the stack is empty.
`iterator`	Returns an iterator for the stack, suitable for use in a for loop (e.g. for value in stack:iterator() do ... end).
`peek`	Returns the value at the top of the stack.
`pop`	Pops the value from the top of the stack.
`push`	Pushes a value onto the stack.

#Stack:clear

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function Stack:clear()

Empties the stack, removing every value and resetting its size to 0.

#Stack:filter

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function Stack:filter(predicate: fun( item: T ): boolean)

Removes every item for which predicate returns true, keeping the order of the remaining items.

Parameters

Name	Type	Description
`predicate`	`fun( item: T ): boolean`	The function that decides whether a frame is removed.

#Stack:isEmpty

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function Stack:isEmpty(): boolean

Checks if the stack is empty.

Returns

Type	Name	Description
`boolean`	`is_empty`	Returns `true` if the stack has no values, otherwise `false`.

#Stack:iterator

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function Stack:iterator(): (fun( self: Stack<T> ): T | nil), Stack<T>

Returns an iterator for the stack, suitable for use in a for loop (e.g. for value in stack:iterator() do ... end). Iterating pops values off the stack one at a time until it is empty, so this consumes the stack.

Returns

Type	Name	Description
`fun( self: Stack<T> ): T \| nil`	`iterator`	The iterator function; calling it pops and returns the next value, or `nil` once the stack is empty.
`Stack<T>`	`stack`	The stack being iterated over, passed as state to the iterator function.

#Stack:peek

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function Stack:peek(): T | nil

Returns the value at the top of the stack.

Returns

Type	Name	Description
`T \| nil`	`value`	The value at the top of the stack, or `nil` if the stack is empty.

#Stack:pop

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function Stack:pop(): T | nil

Pops the value from the top of the stack.

Returns

Type	Name	Description
`T \| nil`	`value`	The value that was removed from the stack, or `nil` if the stack is empty.

#Stack:push

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function Stack:push(value: T): integer

Pushes a value onto the stack.

Parameters

Name	Type	Description
`value`	`T`	The value to push onto the stack.

Returns

Type	Name	Description
`integer`	`position`	The position of the value in the stack.