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Dec 2nd, 2008

Using string as char array

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How would I delete one char from a string?

C++ Syntax (Toggle Plain Text)
string aWord = "question?";
 
while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		delete[i]aWord;
    i++;
  }
string aWord = "question?";

while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		delete[i]aWord;
    i++;
  }

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JackDurden

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Dec 2nd, 2008

Re: Using string as char array

Click to Expand / Collapse Quote originally posted by JackDurden ...

How would I delete one char from a string?
C++ Syntax (Toggle Plain Text)
string aWord = "question?";
 
while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		delete[i]aWord;
    i++;
  }
string aWord = "question?"; while(aWord[i]) { if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]); else delete[i]aWord; i++; }

Use the replace function from string:

http://www.cplusplus.com/reference/s...g/replace.html

C++ Syntax (Toggle Plain Text)
string aWord = "abcdef";
aWord.replace (3, 1, "");
string aWord = "abcdef";
aWord.replace (3, 1, "");

aWord now contains "abcef";

Edit: Or just use erase:

C++ Syntax (Toggle Plain Text)
aWord.erase (3, 1);
aWord.erase (3, 1);

Has the same effect.

Last edited by VernonDozier; Dec 2nd, 2008 at 3:45 pm.

VernonDozier

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Dec 2nd, 2008

Re: Using string as char array

Note you can use find() or find_first_of() etc to get the index of the character youare after.

Chris

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Dec 2nd, 2008

Re: Using string as char array

Well that sort of works but if the char I want to delete/erase is at the end of the string my compiler crashes. I dont understand how to delete/erase a char that is not an alphanumeric type.

C++ Syntax (Toggle Plain Text)
  int i=0;
 string aWord = "abcdf!";
 
while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		aWord.erase (i, 1);
    i++;
  }
  cout<<aWord;
  int i=0;
 string aWord = "abcdf!";

while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		aWord.erase (i, 1);
    i++;
  }
  cout<<aWord;

Last edited by JackDurden; Dec 2nd, 2008 at 3:56 pm.

JackDurden

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Dec 2nd, 2008

Re: Using string as char array

Click to Expand / Collapse Quote originally posted by JackDurden ...

How would I delete one char from a string?
C++ Syntax (Toggle Plain Text)
string aWord = "question?";
 
while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		delete[i]aWord;
    i++;
  }
string aWord = "question?"; while(aWord[i]) { if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]); else delete[i]aWord; i++; }

I can give you two ways. one through STL & other through using the strings only

cpp Syntax (Toggle Plain Text)
       string strWord = "Hello, World!";
	string strResult = "";
 
	for(size_t idx = 0; idx < strWord.size(); ++idx) {
		if (isalpha(strWord[idx])) {
			strResult += strWord[idx];
		}
	}
	cout<< strResult<<endl;
       string strWord = "Hello, World!";
	string strResult = "";

	for(size_t idx = 0; idx < strWord.size(); ++idx) {
		if (isalpha(strWord[idx])) {
			strResult += strWord[idx];
		}
	}
	cout<< strResult<<endl;

Another Way

cpp Syntax (Toggle Plain Text)
  string strWord = "Hello, World! Laiq?";
	size_t pos = 0;
 
	for(size_t idx = 0; idx < strWord.size(); ++idx) {
		if (isalpha(strWord[idx])) {
			strWord[pos] = strWord[idx];
			++pos;
		}
	}
	strWord.resize(pos);
 
	cout<< strWord <<endl;
  string strWord = "Hello, World! Laiq?";
	size_t pos = 0;

	for(size_t idx = 0; idx < strWord.size(); ++idx) {
		if (isalpha(strWord[idx])) {
			strWord[pos] = strWord[idx];
			++pos;
		}
	}
	strWord.resize(pos);

	cout<< strWord <<endl;

Little more tricky.

cpp Syntax (Toggle Plain Text)

   Check the remove_if (...)

Hope the above techniques might help you in understanding ?

Laiq Ahmed

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Dec 2nd, 2008

Re: Using string as char array

Click to Expand / Collapse Quote originally posted by JackDurden ...

Well that sort of works but if the char I want to delete/erase is at the end of the string my compiler crashes. I dont understand how to delete/erase a char that is not an alphanumeric type.
C++ Syntax (Toggle Plain Text)
  int i=0;
 string aWord = "abcdf!";
 
while(aWord[i])
	{
	if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]);
	else
		aWord.erase (i, 1);
    i++;
  }
  cout<<aWord;
int i=0; string aWord = "abcdf!"; while(aWord[i]) { if(isalpha(aWord[i]))printf ("character %c is alphabetic\n",aWord[i]); else aWord.erase (i, 1); i++; } cout<<aWord;

Your program ran for me. I don't know what error you got, but if it is an index-out-of-range/segmentation fault error, you may want to change this:

C++ Syntax (Toggle Plain Text)
while (aWord[i])
while (aWord[i])

C++ Syntax (Toggle Plain Text)
while (i < aWord.length ())
while (i < aWord.length ())

That might make a difference, might not. As to your other problem, only increment i if aWord[i] is a letter. erase and replace will cause the indexes to change, so some characters will be skipped if you use erase/replace AND increment i.

VernonDozier

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Dec 2nd, 2008

Re: Using string as char array

Check the size..

C++ Syntax (Toggle Plain Text)
 
int i=0;
string aWord = "abcdf!";
 
while(aWord[i])
{
   if(isalpha(aWord[i]))
      printf ("character %c is alphabetic\n",aWord[i]);
   else
   {
	aWord.erase (i, 1);
      //..Is idx > length
       if(i>aWord.size())
          break;
       i--;
   }
   i++;
}
cout<<aWord;
  
int i=0;
string aWord = "abcdf!";

while(aWord[i])
{
   if(isalpha(aWord[i]))
      printf ("character %c is alphabetic\n",aWord[i]);
   else
   {
	aWord.erase (i, 1);
      //..Is idx > length
       if(i>aWord.size())
          break;
       i--;
   }
   i++;
}
cout<<aWord;

Last edited by cikara21; Dec 2nd, 2008 at 5:34 pm.

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