isdigit

[John]

I only want a user to input numbers - does C++ have some sort of try-catch? I came across isdigit(), but I believe that is to check whether a character is a number. I came up with this that works excellent to check if a string contains all numbers

int main () {
     bool isString = false;
     string x;
 
     cout << "Enter a number: ";
 
     cin >> x;
     for(int i = 0; i < x.length(); i++) {
          if (!isdigit(x[i])) {
              isString = true;
         }
     }
 
     return 0;
 
} 

But once its done, its still a string and I cant use it to perform math operations on. Can I cast it to an integer? Is there a better way to accomplish this?

[upredsun]

you can use sprintf function to cast string to an integer.

[v0id]

I would rather use std::stringstream, now when we're playing around with std::strings anyway.

template <typename Type>
Type Convert(std::string String)
{
        Type Variable;
        std::stringstream SS(String);
        SS >> Variable;
        return Variable;
}

This takes a string and spits it out into whatever type you're specifying. To spit it out as an integer, then you shall do like this:

std::string String = "1234";
int Number = Convert<int>(String);

[G_Morgan]

C++ has try catch yes but it isn't used all that much (people prefer C style return values).

try {
  throw 1;
} catch (int i) {
  cout << i << "\n";
} 

You can throw just about any type. Java exceptions are generally just glorified strings, you could just throw a string in C++.

[dargueta]

#include <math.h>
using namespace System;
 
//this function can handle unsigned numbers in any radix from 1 to 26.
unsigned __int32 StrToNum(char *Str,unsigned int base)
{
    char *BaseStr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    unsigned __int32 Num = 0,currpow,strsz = 0;
   //get string size
    while(Str[strsz] != '\0')
        ++strsz;
    for(currpow = strsz - 1; currpow >= 0; --currpow)
    {
        if(InStr(BaseStr,Str[strsz - currpow - 1]) != -1)
            Num += (unsigned __int32)(InStr(BaseStr,Str[strsz - currpow - 1]) * pow((double)base,(int)currpow));
        else
            throw gcnew System::ArgumentException("Not a number!");
    }
    return Num;
}
 
signed __int32 InStr(char *Str,char SearchChar)
{
    signed __int32 i = 0;
    while(Str[i] != '\0')
    {
        if(Str[i] == SearchChar)
            return i;
        else
            ++i;
    }
    return -1;
}