Removing whitespace from inside the string

Here's another version:

void Trim(std::string& str, const std::string & ChrsToTrim = " \t\n\r", int TrimDir = 0)
     {
          size_t startIndex = str.find_first_not_of(ChrsToTrim);
          if (startIndex == std::string::npos){str.erase(); return;}
          if (TrimDir < 2) str = str.substr(startIndex, str.size()-startIndex);
          if (TrimDir!=1) str = str.substr(0, str.find_last_not_of(ChrsToTrim) + 1);
     }

     inline void TrimRight(std::string& str, const std::string & ChrsToTrim = " \t\n\r")
     {
          Trim(str, ChrsToTrim, 2);
     }
     
     inline void TrimLeft(std::string& str, const std::string & ChrsToTrim = " \t\n\r")
     {
          Trim(str, ChrsToTrim, 1);
     }

Axter:
How to invoke these functions in main() in your second example?

In the first example, your trim function doesn't remove space from inside the string. That's what I am trying to accomplish.

Or that:

string removeWhitespace(const string& str)
{
       string s;
       for (int i = 0; i < str.length(); ++i)
             if ((unsigned char)str[i] >= (unsigned char)' ')
                  s += str[i];
       return s;
}

Regards, Alex

Correction:

 if ((unsigned char)str[i] > (unsigned char)' ')

it should be

if ((unsigned char)str[i] > (unsigned char)"  ")

itsmeandnobodyelse:

when I use your removeWhitespace function inside the while loop, I get empty lines in the output.

while(getline(sin,line)){

            //Calculate a number of lines
            line_count++;
            
            //remove whitespaces
            line = trim(line);
            
            //skip empty lines
            if (line.empty())
                  continue;

            line=removeWhitespace(line);

            cout  << line << endl;

       
      }

That works ok here:

string removeWhitespace(const string& str)
{
    string s;
    for (int i = 0; i < str.length(); ++i)
        if ((unsigned char)str[i] > (unsigned char)' ')
            s += str[i];
        return s;
}

int main() {
   
   string s = "     A   B ( C)    D     ";
   s = removeWhitespace(s);
   cout << s << endl;

   return 0;
}

Thank you, guitaristx !

>> when I use your removeWhitespace function inside the while loop, I get empty lines in the output.

In your code sample, you used trim() function *and* removeWhitespace(), so I cannot say what happened.

Regards, Alex

Hi Alex,

I tried different combinations: only with trim, only with removeWhitespace and both.
Every time I used removeWhitespace it would produce empty strings.

What was more surprising is that when in removeWhitespace I set a condition not equal space, it printed to the screen my string unchaged char by char. So, this function somehow failed to recognize the space.

 if ((unsigned char)str[i] != (unsigned char)" ")

However, removeWhitespace worked on a single string, in main(), with double quotes for the space. But when I changed double quotes to single quotes it didn't work.

Anyway, guitaristx's solution worked like a charm and saved me from mental exhaustion :) This problem seemed to be so easy in the beginning...

>>  if ((unsigned char)str[i] != (unsigned char)" ")

This doesn't work because you're typecasting a const char* as an unsigned char, which will more than likely do pointer truncation, and you'll have no freakin' idea what value it's going to use.  Try this:

if (str[i] != ' ')//notice the single quote rather than the double quote

itsmeandnobodyelse:
Sorry for the mishap. I just tried guitaristx's suggestion in the last comment. Your solution also works. I made a mistake with double quotes.

itsmeandnobodyelse:
I can give you 50 points but I don't know how. I already accepted the answer.

Hi, njava

Thanks that you tested my solution again. It was less frustrating getting no points than being mistakenly judged.

>> I can give you 50 points but I don't know how

If you would like to give additional points, you could open a new question titled 'points for ...', and accept an appropriate answer to that.

Regards, Alex

Alex:
here is the link to your 50 points

http://www.experts-exchange.com/Programming/Programming_Languages/Cplusplus/Q_21282983.html

Can you use strtok....

char *s1, *s2;

s1 = strtok(str," ");
while( (s2 = strtok(NULL," ")) != NULL)
{
   strcat(s1,s2);
   memset(s2,0,strlen(s2));
}


Soemthing like this... This will remove all spcases before, in the middle and also trailing the string...
Of course the above need to have some error checks....

static bool
strip(const char c)
{return (c == ' ' || c == '\t');}

//...
std::string s ("whatever");
//...
s.erase(std::remove_if(s.begin(),s.end(),strip),s.end());

Your doing it the hard way. The following two lines will
remove the spaces from everywhere.
 
#include <algorithm>

string::iterator junkI = remove(str.begin(),str.end(),' ');
str.erase(junkI,str.end()); // Make sure you remove the junk left at the end of the string