TRIM in c++

[Daok]

I know that in java and in VB string have something .trim() but in C++ what is the name for "trim"?

[Daok]

trim take out space... like " allo " will be : "allo"

[Technocrat]

I am going to guess you want to trim a string. Here is the solution I came up with

/*##############################################################################################*/

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
//| Function:    Trim()
//|                    Overload Function
//| In:            string *stString
//|                    In String
//| Return:        None
//| Notes:        This Function Trims Spaces From The Begining And The End Of A String
//|                This Function Was Created By jim mcnamara on VB-World.net Forums
//| Example:    string p = "    TTTT    ";
//|                Trim(p);            //Should Chang p To "TTTT"
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

void Trim(string *stString)
{
    RTrim(stString);
    if (stString->length())
        LTrim(stString);
}


/*##############################################################################################*/

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
//| Function:    RTrim()
//|                    Overload Function
//| In:            string stString
//|                    In String
//| Return:        None
//| Notes:        This Function Trims Spaces From The End Of A String
//| Example:    string p = "TTTT    ";
//|                RTrim(p);            //Should Chang p To "TTTT"
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

void RTrim(string *stString)
{
/*>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>*/
    int i;                            //Count VAR
/*<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<*/

    if (!stString->length())                    //If There Is No Length
        return;

    i = stString->length()-1;                    //Set The Counter To The String Length -1

    while (stString->substr(i,1) == " ")        //While There Is Still " "
    {
        *stString = stString->substr(0, i);        //Remove Off The End Of The String
        i--;                                    //Advance The Counter
    }

}

/*##############################################################################################*/

/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
//| Function:    LTrim()
//|                    Overload Function
//| In:            string *stString
//|                    In String
//| Return:        None
//| Notes:        This Function Trims Spaces From The Front Of A String
//| Example:    string p = "    TTTT";
//|                LTrim(p);            //Should Chang p To "TTTT"
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

void LTrim(string *stString)
{
/*>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>*/
    int i;                            //Count VAR
    string buf;                        //Temp String VAR
/*<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<*/

    if (!stString->length()) return;                        //If The Length Is 0

    i = 0;                                                    //Setup The Counter VAR

    while (stString->substr(i,1) == " ")                    //While " "
        i++;                                                //Increase Counter

    if (i == stString->length())                            //If The Whole String Is " "
    {
        *stString = "";                                        //Return Blank String
        return;
    }

    try
    {
        *stString = stString->substr(i,stString->length()-i);    //Send The String Back Without The Spaces
    }
    catch(...)
    {
        *stString = "";                                        //Return Blank String
        return;
    }

} 

[parksie]

Two comments:

1. References rather than pointers, safer and easier

2. In my version of a trim function, I used isspace rather than checking for just spaces...personal preference but you might find it useful.

[Technocrat]

Can you give me a quicky example of how you would use a referance?

[parksie]

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

string trim(const string &str) {
	string::const_iterator start, end;

	for(start = str.begin(); start != str.end(); ++start) {
		if(!isspace(*start)) break;
	}

	for(end = str.end() - 1; end != str.begin(); --end) {
		if(!isspace(*end)) break;
	}

	return string(start, end + 1);
}

int main() {
	string s("    \t\n  Hello there      ");
	cout << "blah:" << trim(s) << ":thingie" << endl;
}

That's a method that returns a new string, to trim it in-place, try this:

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

void trim(string &str) {
	string::iterator start, end;

	for(start = str.begin(); start != str.end(); ++start) {
		if(!isspace(*start)) break;
	}

	for(end = str.end() - 1; end != str.begin(); --end) {
		if(!isspace(*end)) break;
	}

	str.assign(start, end + 1);
}

int main() {
	string s("    \t\n  Hello there      ");
	trim(s);
	cout << "blah:" << s << ":thingie" << endl;
}

[Technocrat]

ahh, I see. Never thought of that.