Pseudo-coding an N-iterative loop

[wasabi]

I am currently needing to create a loop that deals with N iterators. The real purpose is to create a series of names which will then be used to open files with such names. But anyways...

For example, imagine you have an input such as

A%B%C% (1 2 3) (4 5) (6)

The program should then create the following names:

A1B4C6
A1B5C6
A2B4C6
A2B5C6
A3B4C6
A3B5C6

That is, the % is a placeholder for the values in each parentheses.

In this case, the best loop would be (in pseudo-code)

for (each A)
   for(each B)
      for(each C)
         CreateName();

However, that is hard-written as a three-iterator loop. What if the filename is only "A%B%"? What if it's a crazy "A%B%C%D%E%F%G%"?

I've tried writing something like

for(each position)
   for(each position after this position)
      for(each value of the position)
         CreateName();

But it doesn't seem to work. To keep things a bit more realistic, here's my actual code:

for(i=count-2;i>=0;i--)
{
	for(int j=count-1;j>i;j--)
	{
		stringstream _substr(substr[j]);
		string value;
		while(_substr >> value)
		{
			name.replace(pos[j],1,value);
			cout << name << endl;
		}
	}
}

Where substr contains all the values of each parentheses ( 1 2 3 and 4 5 and 6 in different strings) and name contains the "first value" (A1B4C6)

However, this doesn't work. It loops too much in the beginning, repeating itself, and loops too little in the end.

[hamsterman]

Here's something:

#include <iostream>

template<int N>
struct iterator{
    iterator<N>* max;
    int val[N];

    iterator() : max(0){
        memset(val, 0, N*sizeof(int));
    }
    bool operator ++(){
        if(!max) return 0;
        val[0]++;
        for(int i = 0; i < N; i++){
            if(val[i] >= max->val[i]){
                if(i < N-1){
                    val[i+1]++;
                    val[i] = 0;
                }else return 0;
            };
        }
        return 1;
    }
};

int main(){
    iterator<3> max;
    max.val[0] = 2;
    max.val[1] = 5;
    max.val[2] = 3;

    iterator<3> i;
    i.max = &max;

    do{
        std::cout << "A" << i.val[0] << "B" << i.val[1] << "C" << i.val[2] << '\n';
    }while(++i);
    std::cin.get();
    return 0;
}

You could make it more flexible: with non constant size, minimum values, and so on, but I'm a little too lazy for that.

[naivnomore]

Here is a quick implementation. Remember, I have not done any error checking & the solution uses recursion. The crux of the implementation is in the replace recursive method.

#include <iostream>
#include <string>
#include <vector>
#include <iterator>
#include <sstream>
using namespace std;

void replace(const string& s, vector<vector<char> >& vreps, int index);

int main()
{
	string sInput = "A%B%C% (1 2 3) (4 5) (6)", sToken;
	cout << "Input: " << sInput << endl;
	vector<string> vs;

	// Tokenize string
	// A%B%C%
	// 1 2 3
	// 4 5
	// 6

	string::size_type fpos = sInput.find(" ("), spos = 0;
	while (fpos != string::npos){
		if (sInput[fpos - 1] == ')')
			sToken = sInput.substr(spos, fpos - spos - 1);
		else
			sToken = sInput.substr(spos, fpos - spos);
			
		vs.push_back(sToken);
		spos = fpos + 2;
		fpos = sInput.find(" (", spos);
	}
	if (spos < sInput.size())
		vs.push_back(sInput.substr(spos, sInput.size() - spos - 1));
	
	// Create the replacement vector which is a vector of vector of chars with the replacement values

	vector<vector<char> > vreps(vs.size()-1);
	for (vector<string>::size_type i = 1; i < vs.size(); ++i){
		istringstream ss(vs[i]);
		char c;
		while (ss >> c){
			vreps[i-1].push_back(c);
		}
	}

	// Invoke replace with A%B%C% & the replacement vector
	cout << "Output: " << endl;
	replace(vs[0], vreps, 0);
}

void replace(const string& s, vector<vector<char> >& vreps, int index)
{
	string sTmp = s;
	string::size_type fpos = s.find("%");
	if (fpos != string::npos){
		for (vector<vector<char> >::size_type i=0; i < vreps[index].size(); ++i){
			sTmp.replace(fpos, 1, string(1, vreps[index][i]));
			replace(sTmp, vreps, index + 1); // Recursive call to replace
		}		
	}
	else
		cout << s << endl;
}

[wasabi]

Many thanks naivnomore, that worked like a charm. I had to make a few alterations to make it error-safe (in case the user didn't input all the variables or if there were no variables, for example) but that worked out amazingly well.