Convert separate digits into one whole number C++ - c++

Question

I need a little more help. I have managed to convert all my chars input from a text file into digits.
Example:
Input from file:
$1,9,56#%34,9
!4.23#$4,983
Output:
1956
349
423
4983
Now, I need to take those individual digits the 1 9 5 6 and make it read as a whole number. The output would look the same but they would actually be whole numbers. Make sense? I have to do this in my outer loop. It also has to be an EOF loop. So, I know I need to take the first digit and multiply it by 10 and add the next digit then multiply all that by 10 until I reach the last number. How can I write that in an efficient non-crashing way?
The input.txt file has the input stated above.
This is what I have so far...
Any help is greatly appreciated
/*
*/
//Character Processing Algorithm
#include <fstream>
#include <iostream>
#include <cctype>
using namespace std;
char const nwln = '\n';
int main ()
{
ifstream data;
ofstream out;
char ch;
char lastch;
int sum;
data.open ("lincoln.txt"); //file for input
if (!data)
{
cout << "Error!!! Failure to Open lincoln.txt" << endl;
system ("pause");
return 1;
}
out.open ("out.txt"); //file for output
if (!out)
{
cout << "Error!!! Failure to Open out.txt" << endl;
system ("pause");
return 1;
}
data.get (ch); // priming read for end-of-file loop
while (data)
{
sum = 0;
while ((ch != nwln) && data)
{
if (isdigit(ch))
out<<ch;
if (ch == '#')
out<<endl;
{
;
}
lastch = ch;
data.get (ch); // update for inner loop
} // inner loop
if (lastch != '#')
out<<endl;
data.get (ch); // update for outer loop
} //outer loop
cout << "The End..." << endl;
data.close (); out.close ();
system ("pause");
return 0;
} //main

Answer 1

If you need simply to output all numbers in the standard stream std::cout (or some other stream as for example file) then you can use the following code as an example. I only substituted the file input for std::cin input in variable line. You can use file input instead of the standard stream.
Also instead of
std::ostream_iterator<char>( std::cout ),
use
std::ostream_iterator<char>( out ),
and instead of
std::cout << std::endl;
use
out << std::endl;
after the std::copy_if call.
Here is the example
#include <iostream>
#include <iterator>
#include <string>
#include <sstream>
#include <algorithm>
#include <cctype>
int main()
{
std::string line;
while ( std::getline( std::cin, line) ) // instead of std::cin use data
{
// std::cout << line << std::endl;
std::string word;
std::istringstream is( line );
while ( std::getline( is, word, '#' ) )
{
// std::cout << word << std::endl;
auto it = std::find_if( word.begin(), word.end(),
[]( char c ) { return ( std::isdigit( c ) ); } );
if ( it != word.end() )
{
std::copy_if( it, word.end(),
std::ostream_iterator<char>( std::cout ),
[]( char c ) { return ( std::isdigit( c ) ); } );
std::cout << std::endl;
}
}
}
}
Test input data is
$1,9,56#%34,9
!4.23#$4,983
The output is
1956
349
423
4983
Or you can define the lambda before its using.
#include <iostream>
#include <iterator>
#include <string>
#include <sstream>
#include <algorithm>
#include <cctype>
int main()
{
std::string line;
while ( std::getline( std::cin, line) ) // instead of std::cin use data
{
// std::cout << line << std::endl;
std::string word;
std::istringstream is( line );
while ( std::getline( is, word, '#' ) )
{
// std::cout << word << std::endl;
auto lm_IsDigit = []( char c ) { return ( std::isdigit( c ) ); };
auto it = std::find_if( word.begin(), word.end(), lm_IsDigit );
if ( it != word.end() )
{
std::copy_if( it, word.end(),
std::ostream_iterator<char>( std::cout ),
lm_IsDigit );
std::cout << std::endl;
}
}
}
}

Answer 2

Read the input file character by character. To check if a character is a digit, use std::isdigit. Then add the number to the back of a string.
If you need to convert a string to an integer, use std::stoi