A calculator for expressions with predefined grammar, including basic calcualtions, let statements, if statements, and function calls. The expressions can be typed in or imported from existing files.

1. Add: <expression1> + <expression2>
2. Multiply: <expression1> * <expression1>
3. Variable (only accept alphabetic words): , x, var, ...
4. Let: _let x = 3 _in x + 1, ...
5. Bool: _true & _false, ...
6. Comparison: <expression1> == <expression2>
7. If: _if _true _then 0 _else 1, _if x == 5 _then x + 1 _else x,
8. Function: _fun(x) x + 1, ...
9. Function call: (_fun(x) x + 1)(1), _let f = _fun(x) x + 1 _in f(1), ...

1. clone the repo: git clone https://github.com/Sonia-96/Expression_Calculator_in_CPP
2. open Calculator/Calculator.pro file

Calculate the result of an expression. For example, the result of Fibonacci(10) is 55.

Print an expression in a nicer format. In the following example, the statements will be aligned and the redundant brackets will be removed through Pretty Print mode.