constexpr-calculator

Constexpr-enabled interpreter of math expression developed in C++23

Prerequisites

• g++ 14.2 or newer
• cmake 3.20 or newer

Capabilities

This calculator accepts the most important mathematical operators/functions:

• +, -, *, /
• ( and )
• ^ power
• ! factorial
• abs, floor, ceil

Build

Your CMakeLists.txt should contain the following lines:

    add_subdirectory(path-to-constexpr-calculator) # external/.../constexpr-calculator

    add_executable(MyApp my-files-to-build) # main.cpp file1.cpp ...
    target_link_libraries(MyApp PRIVATE calc) # calc is the name of the library

To build and run only the librarys' tests, do the following:

    # clone
    > git clone https://github.com/simone3c/constexpr-calculator.git --recurse-submodules

    # build
    > cmake -B build -DBUILD_TESTS=ON
    > cmake --build build

    # run
    > build/calc_test

Usage

The evaluation can be performed at compile time:

// constexpr usage

#include "calculator.hpp"

int main(){
    constexpr auto expr = "1+1.5";
    constexpr auto val = calc::evaluate(expr);

    static_assert(val.value() == 2.5);
}

but also at runtime if needed:

// NON-contexpr usage

#include "calculator.hpp"

int main(){
    auto expr = user_input();
    auto val = calc::evaluate(expr);

    assert(val.value() == 2);
}

Errors can be easily printed:

#include <print>
#include "calculator.hpp"

int main(){
    constexpr auto expr = "1+ error here"; 
    constexpr auto val = calc::evaluate(expr);

    static_assert(!val.has_value());

    std::println("{}", val.error());
}

TODO

• math functions
• definite intgrals
• summation and product notation
• change grammar to force writing "x-(-4)" insted of "x--4"
• complex numbers
• automatically deduce the evaluation type