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std::stack<T,Container>::push

From cppreference.com
< cpp‎ | container‎ | stack
 
 
 
 
void push( const value_type& value );
void push( value_type&& value );
(since C++11)

Pushes the given element value to the top of the stack.

1) Effectively calls c.push_back(value).
2) Effectively calls c.push_back(std::move(value)).

Contents

[edit] Parameters

value - the value of the element to push

[edit] Return value

(none)

[edit] Complexity

Equal to the complexity of Container::push_back.

[edit] Example

This program implements the BrainHack DSL, when the use of std::stack is an idiomatic way to process paired brackets.

#include <array>
#include <cstdint>
#include <iostream>
#include <map>
#include <stack>
#include <stdexcept>
#include <string_view>
 
class BrainHackInterpreter
{
    std::map<unsigned, unsigned> open_brackets, close_brackets;
    unsigned program_pos_{0};
    std::array<std::uint8_t, 32768> data_;
    int data_pos_{0};
 
    void collect_brackets_positions(const std::string_view program)
    {
        std::stack<unsigned> brackets_stack;
 
        for (auto pos{0U}; pos != program.length(); ++pos)
        {
            const char c{program[pos]};
            if ('[' == c)
                brackets_stack.push(pos);
            else if (']' == c)
            {
                if (brackets_stack.empty())
                    throw std::runtime_error("brackets [] do not match!");
                else
                {
                    open_brackets[brackets_stack.top()] = pos;
                    close_brackets[pos] = brackets_stack.top();
                    brackets_stack.pop();
                }
            }
        }
 
        if (!brackets_stack.empty())
            throw std::runtime_error("brackets [] do not match!");
    }
 
    void check_data_pos(int pos)
    {
        if (pos < 0 || pos >= static_cast<int>(data_.size()))
            throw std::out_of_range{"data pointer out of bound"};
    }
 
public:
    BrainHackInterpreter(const std::string_view program)
    {
        collect_brackets_positions(program);
        data_.fill(0);
 
        for (; program_pos_ < program.length(); ++program_pos_)
            switch (program[program_pos_])
            {
                case '<':
                    check_data_pos(--data_pos_);
                    break;
                case '>':
                    check_data_pos(++data_pos_);
                    break;
                case '-':
                    --data_[data_pos_];
                    break;
                case '+':
                    ++data_[data_pos_];
                    break;
                case '.':
                    std::cout << data_[data_pos_];
                    break;
                case ',':
                    std::cin >> data_[data_pos_];
                    break;
                case '[':
                    if (data_[data_pos_] == 0)
                        program_pos_ = open_brackets[program_pos_];
                    break;
                case ']':
                    if (data_[data_pos_] != 0)
                        program_pos_ = close_brackets[program_pos_];
                    break;
            }
    }
};
 
int main()
{
    BrainHackInterpreter
    {
        "++++++++[>++>>++>++++>++++<<<<<-]>[<+++>>+++<-]>[<+"
        "+>>>+<<-]<[>+>+<<-]>>>--------.<<+++++++++.<<----.>"
        ">>>>.<<<------.>..++.<++.+.-.>.<.>----.<--.++.>>>+."
    };
    std::cout << '\n';
}

Output:

Hi, cppreference!

[edit] See also

(C++11)
constructs element in-place at the top
(public member function) [edit]
removes the top element
(public member function) [edit]