C++ Questions

[AtkinsSJ]

In order to not unfairly hijack Ducky's thread, I thought I'd create a new topic for me to ask my fairly-regular questions on how to do stuff in C++.

Firstly, is there a built-in function for converting an integer to a string? If not, I could always try to write one myself, but a ready-made function would be very helpful.

[SpaceManiac]

As far as I know, there isn't, but this should work well. Put it in a file, say num2string.h

PHP Code:

#include <string>
namespace num2string {
    typedef unsigned long int BigNum;
    typedef unsigned int Num;
 
    std::string numbers[] = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
 
    BigNum power(int base, int exp)
    {    // this works for normal cases with positive exponents
        if(exp == 0) return 1;            // x^0 = 1
        if(exp == 1) return base;        // x^1 = x
        return base * power(base,exp-1);
    }
 
    std::string num2string(int n) {
        std::string str = (n < 0 ? "negative " : "");
        Num num = (n < 0 ? -n : n);
        Num y;
        for(y = 0; power(10,y) <= num; y++);
        // y now contains the highest power plus 1
        for(Num p = y - 1; p >= 0; p--)
        {
            // calculate digit
            int x = (num / power(10,p)) % 10;
            // add to string
            str += numbers[x] + " ";
    /* this is necessary; an unsigned long will wrap around and become a very large number
       (which IS >= 0), causing infinite looping. However, in this case it never gets that
       far because 10^(maximum unsigned long value) will always overflow! */
            if (p == 0) break;
        }
        return str.trim();
    }
} 


A simple program using this code might resemble the following.

PHP Code:

#include <string>
#include <iostream>
#include "num2string.h"
using namespace std;
 
int main()
{
    int num;
    string str;
    cin >> num;
    str = num2string::num2string(num);
    cout << str;
    return 0;
} 


Thanks to Mr.Onion for the tip on str.trim()!

[Jamul]

But there is... sprintf!

[SpaceManiac]

Ah yes, my solution is for numbers to words. If you just need character representations, Jamul's idea is best.

sprintf(buffer,"%d",num);

I think that's how it works... I don't use the C standard library much. Just the C++ one (yay std::string!)

[Ducky]

Originally Posted by Jamul

But there is... sprintf!

Aww...Atkins...Jamul posted in your thread. Lucky guy. LOL

-Ducky (VENI, VIDI, ROLEX...I came, I saw, - what time it was!)

[AtkinsSJ]

Oh, cool! I didn't realise you could print to something other than the screen. Thanks.

[Ducky]

Originally Posted by AtkinsSJ

Oh, cool! I didn't realise you could print to something other than the screen. Thanks.

Oh yeah..there is even fprintf (To print to files!)

- Ducky (VCRs are irrelevant. - Locutus of RCA)