variables.cpp

#include <string>
#include <iostream>
#include <map>

typedef std::map<std::string, std::string> Defines;

bool evaluate(const Defines& defines, std::string *value) {
    std::string::reverse_iterator i = value->rbegin();
    std::string::iterator         e = value->end();
    while (i != value->rend()) {
        if (*i == '}') {
            e = i.base() - 1;
            i++;
        } else if (*i == '{') {
        	if (e == value->end()) {
        		return false; 
        	}
            const std::string::iterator     b = i.base() -1;
            const std::string				v(b + 1, e);
            const Defines::const_iterator   p = defines.find(v);
            if (p != defines.end()) { 
                value->replace(b, e + 1, p->second);
            } else {
            	return false; // or value->erase(b - 1, e);
            }
            i = value->rbegin();
            e = value->end();
        } else {
			i++;
        }
    }
    return e == value->end();
}

int main()
{
	{
        Defines d;
        std::string s = "hello world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        d["1"] = "my";
        d["2"] = "test";
        d["3"] = "string";

        std::string s = "{1} {2} {3}";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        d["world"]   = "1";
        d["hello 1"] = "my";

        std::string s = "here is {hello {world}} string";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        d["world"]   = "this";

        std::string s = "here is {world} string";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        d["world"]   = "1";

        std::string s = "here is {hello {world}} string";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello { world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello } world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello world}";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello world{";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "{hello world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "}hello world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello {{world";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    {
        Defines d;
        std::string s = "hello world{{";
        std::cout << (evaluate(d, &s) ? "pass":"fail") << ": " << s << std::endl;
    }
    return 0;
}