C++ 将字符串逻辑表达式转换为条件表达式

Question

I have a logical expression in string and need to evaluate. Is there a way in C++ do it?

std::string exp = "(1||0)&&(1&&1)&&(1||0&&0)";

Eg:

if ((1 || 0) && (1 && 1) && (1 || 0 && 0))
    {
        std::cout << "true\n";
    }

Answer 1

There's no easy built-in way in C++ to evaluate logic expressions like that. If you want to evaluate such an expression in runtime, you need to parse a string into some intermediate representation first (eg an expression tree) by writing a parser and write an evaluator that will flatten that tree into a single value.

Then, assuming

struct ExprTree { ... };
ExprTree parse(std::string const& input);
bool eval(ExprTree const& expr);

you can get the result of such a string expression with

std::string exp = "(1||0)&&(1&&1)&&(1||0&&0)";
if (eval(parse(exp)) {
    // ... 
}