Expression evaluator written in C++17 using std::visitor function in the interface of std::variant

The project demonstrates the use of C++17's std::visitor function in the interface of std::variant to implement the visitor pattern in the field of classical design patterns, by the example of an expression evaluator.

Description

• An Expression, here, is an inductively defined object using the atomic Expressions of type int, bool, or std::monostate, together with operators inherited from these types. More technically, an Expression is a self-recursive variant with 1-ary and 2-ary operators defined on it.
• Each Expression is either valid or invalid. An Expression is valid just in case it represents a well-formed formula or mathematical expression (no atomic part of the Expression is of type std::monostate).
• Visitor method typeCheck() checks whether an Expression is well-formed.
• Visitor method evaluate() evaluates the expression or formula.
• Each method defined on the Expression follows the visitor pattern, including the operators +,-, and so on.

Prerequisites

You will need CMake and a compiler that can handle C++17. The very least I recommend is gcc 7.4.0 and CMake 3.2; tested on gcc 7.4.0 and CMake 3.10.2

Building the project

Clone the repository.

git clone https://github.com/wwoloszyn/expressions.git

Enter the cloned project.

cd expressions

Create a build folder and enter this folder.

mkdir build && cd build

Call cmake.

cmake ..

Run make.

make

Running the tests

Run the unit tests by executing the binary file.

./expressions