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/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
file Copyright.txt or https://cmake.org/licensing for details. */
#pragma once
#include "cmConfigure.h" // IWYU pragma: keep
#include <memory>
/** Base class template for CRTP to represent a stack of constant values.
Provide value semantics, but use efficient reference-counting underneath
to avoid copies. */
template <typename T, typename Stack>
class cmConstStack
{
struct Entry;
std::shared_ptr<Entry const> TopEntry;
public:
/** Default-construct an empty stack. */
cmConstStack();
/** Get a stack with the given call context added to the top. */
Stack Push(T value) const;
/** Get a stack with the top level removed.
May not be called until after a matching Push. */
Stack Pop() const;
/** Get the value at the top of the stack.
This may be called only if Empty() would return false. */
T const& Top() const;
/** Return true if this stack is empty. */
bool Empty() const;
protected:
cmConstStack(std::shared_ptr<Entry const> parent, T value);
cmConstStack(std::shared_ptr<Entry const> top);
};