Trim A String

[pittuck]

Hi, as you may no i am working on some serial communications code, to communicate with my elecronics project.

Here is the deal, i have a string:

s654us23us456us234us2us34

Now, the string will always be 2 letters followed by some numbers, but here may be 1, 2 or 3 numbers depending on what is happening.

I can split a string like this:

us23us456us234us2

Into arrays. BUT my problem is with the strings in that the end part may be cut off as with the start.

So if the first 2 characters are letters then the start is fine. If not then the first letter (if there is one) and numbers must be deleted so that the first 2 characters are letters.

The end is different, if a number is present as the last character:

all numbers deleted in reverse order (going back through the string), and then deleting the 2 letters.

If a letter is present at the end then just the letters at the end need deleting.

I have tried myself to do this, but i am within weeks of starting C++ so need any help possible.

I hope i have explained things well enough for you to understand and help me.

Thank You,

- Martyn

[laasunde]

Take a look at this code for the start of the string:

#include <iostream>
#include <string>
#include <ctype.h>
using namespace std;

int main()
{
  string sVar = "s6us23us456us234us2us34";
  cout << "Before = " << sVar << endl;

  if ( isdigit(sVar.at(0)) || isdigit(sVar.at(1)) )
  {
    int count;
    for(count=2; count < sVar.length(); count++)
        if ( isalpha(sVar.at(count)) )
            break;
    
    sVar.erase(0, count);
  }
  cout << "After = " << sVar << endl;
  system("PAUSE");
  return 0;
}

[pittuck]

Thanks,

Thats is very helpful.

How would i got about doing the end bit? Counting backwards for example?

The end bit is the most important becasue us202 could be sent but only us2 recieved, there is a large difference between 2cm and 202cm

Thanks

- Martyn

[pittuck]

Oh and here is the code for the begining:

#include <iostream>
#include <string>
#include <ctype.h>
using namespace std;

int main()
{
  string sVar = "u2us23us456us234us2us34";
  cout << "Before = " << sVar << endl;
  
  if ( isalpha(sVar.at(0)) && isalpha(sVar.at(1)) )
  {
  
  
  
  }else{
  
    if ( isdigit(sVar.at(0)) )
    {
    
        int i;
        while ( isdigit(sVar.at(i)) )
        {
        
                i++;
                
        }
        
        sVar.erase(0, i);
        
    }
    
    if ( isalpha(sVar.at(0)) )
    {
    
        int k;
        while ( isalpha(sVar.at(k)) )
        {
        
                k++;
                
        }
        
        while ( isdigit(sVar.at(k)) )
        {
        
                k++;
                
        }
        
        sVar.erase(0, k);
        
        
    }  
    
  }
  
  cout << "After = " << sVar << endl;
  system("PAUSE");
  return 0;
  
}

[laasunde]

This should get you going:

  int len = sVar.length();
  if ( isdigit(sVar.at(len-1)) )
  {
     cout << "last char is a number..." << endl; 
  }
  else if( isalpha(sVar.at(len-1)) )
  {
   cout << "last char is a letter..." << endl;
  }

Take a look at this page : http://www.cppreference.com/cppstring.html to see how to manipulate a string.

[pittuck]

Thanks,

I will post my *final* code in a few mins, when its final