Command Parser for Game: Any Programming Patterns?

[LeafyCircuits]

Hi, LeafyCircuits here!

Comp Specs:
OS: Windows 7 Home Premium 64-bit
Compiler: MinGW v4.6.2 running C++11
IDE: Code::Blocks v12.11

I've been wanting to create a mini-RPG/other game that uses commands that the user can invoke. For example, I want the user to be able to type something like this:

commandname [ARG1] [ARG2] [...]

And would do something in-game. What I'm wondering is how to accomplish this in code. Actually defining a command that does something is easy enough, but it's actually parsing what the user typed and interpreting that to execute a command is complicated. I know I'll need a basic Tokenizer, so I created one myself:

class _BasicTokenizer
{
public:
    void tokenize(string str, char delimiter=' ')
    {
        string tokenbuf;
        for (int i=0;i<str.length();i++)
        {
            if (str[i]==delimiter)
            {
                tokens.push_back(tokenbuf);
                tokenbuf="";
            }
            else
            {
                tokenbuf+=str[i];
            }
        }
        tokens.push_back(tokenbuf);
    }

    vector<string> returnTokens() {return tokens;}

    vector<string> TokenizeAndReturn(string somestr, char adelimiter=' ')
    {
        tokenize(somestr, adelimiter);
        returnTokens();
    }

private:
    vector<string> tokens;
};

After that, I'm not sure how to approach this. One thing I've tried is creating a class that has all the commands, then create another class that handles the parsing, then calls the appropriate function through the use of function pointers; that got messy pretty quickly. Having a separate typedef for every function with different args and return values would get very cluttered and disorganized. So I scraped this idea, but I feel like I'll need another class to do the parsing at least, I just don't know where to go from here.

So, that leads to one of the things I'm wondering: is there a design pattern for this? I'm sure I'm not the only one to have thought of in-game commands, so maybe there is a basic design pattern, or at least, pattern of thought.

What I'm basically asking is for anybody more experienced in this to help me out :)

Any and all help is appreciated.

[firedraco]

I don't think this is a "pattern" so to speak, but...

In my game, I just read the first word as the action, then passed the rest of the arguments to a function pointer so that the action function could deal with them.

Something like this:

std::map<std::string, std::function<void(std::vector<std::string>)>)>

Of course, this requires all the functions to return the same value, etc, so you might want to have it take a pointer/reference to a "game world" or "player" structure so that you can modify stuff.

[LeafyCircuits]

firedraco said:

then passed the rest of the arguments to a function pointer

Well, where would you have declared those function pointers? And, do you use a parser class, or is this global?

(Would make sense if this were inside a struct or namespace, even a class)

I also understand that most of this stuff is context sensitive. I just say "pattern" because this is a common thing to come across. I assumed a "general idea" sort of thing.

[firedraco]

Well, where would you have declared those function pointers? And, do you use a parser class, or is this global?

The functions were declared globally, although they could be anywhere really.

The pointers were created upon insertion. Like I would have something like this:

command_map["look"] = &look_func;