The type of stacks containing elements of type 'a.

Raised when Stack.pop or Stack.top is applied to an empty stack.

Return a new stack, initially empty.

push x s adds the element x at the top of stack s.

pop s removes and returns the topmost element in stack s, or raises Empty if the stack is empty.

pop_opt s removes and returns the topmost element in stack s, or returns None if the stack is empty.

• since 4.08

top s returns the topmost element in stack s, or raises Empty if the stack is empty.

top_opt s returns the topmost element in stack s, or None if the stack is empty.

• since 4.08

Discard all elements from a stack.

Return a copy of the given stack.

Return true if the given stack is empty, false otherwise.

Return the number of elements in a stack. Time complexity O(1)

iter f s applies f in turn to all elements of s, from the element at the top of the stack to the element at the bottom of the stack. The stack itself is unchanged.

fold f accu s is (f (... (f (f accu x1) x2) ...) xn) where x1 is the top of the stack, x2 the second element, and xn the bottom element. The stack is unchanged.

• since 4.03

Iterate on the stack, top to bottom. It is safe to modify the stack during iteration.

• since 4.07

Add the elements from the sequence on the top of the stack.

• since 4.07

Create a stack from the sequence.

• since 4.07