Thread: parsing words out of a string?

I'm trying to parse the first words out of a string and i've comeup with this:

Code:

#include <string>
#include <iostream>


using namespace std;

int main()
{
	string Input = "/kick name the reason";
	string Command, CommandTarget, CommandData, ParseString;

	ParseString = Input;
	Command = ParseString.substr(0, ParseString.find(" "));
	ParseString = ParseString.substr(ParseString.find(" ")+1);
	CommandTarget = ParseString.substr(0, ParseString.find(" "));
	ParseString = ParseString.substr(ParseString.find(" ")+1);
	CommandData = ParseString;
	cout << "Input: " << Input << endl;
	cout << "Command: " << Command << endl;
	cout << "Target: " << CommandTarget << endl;
	cout << "Data: " << CommandData << endl;

	Input = "/kick name";

	ParseString = Input;
	Command = ParseString.substr(0, ParseString.find(" "));
	ParseString = ParseString.substr(ParseString.find(" ")+1);
	CommandTarget = ParseString.substr(0, ParseString.find(" "));
	ParseString = ParseString.substr(ParseString.find(" ")+1);
	CommandData = ParseString;
	cout << "Input: " << Input << endl;
	cout << "Command: " << Command << endl;
	cout << "Target: " << CommandTarget << endl;
	cout << "Data: " << CommandData << endl;


	system("pause");
	return 0;
}

Would this be a good way to do it? All those calls to find and substr seems like it'd be slower than it needs to.

You can use a stringstream to parse as well. If the words are separated by whitespace, just use operator>>.

Ok, but how would I parse the rest of the string from the stream including whitespaces. Like in the first section of the sample code, "the reason" contains whitespaces but it all needs to go into the CommandData string. In the second section of the sample code, CommandData should be empty. It'll be empty so I can check if anything was sent, but that's all going to be done after the string is parsed.

I rather like this example from the FAQ

Code:

#include <string> 
#include <iostream> 
#include <vector> 
int main(void)
{
  std::string numbers_str = "zero,one,two,three,four,five,six,seven,eight,nine,ten";
  std::vector < std::string > numbers; //we'll put all of the tokens in here 
  std::string  temp;

  while (numbers_str.find(",", 0) != std::string::npos)
  { //does the string a comma in it?
    size_t  pos = numbers_str.find(",", 0); //store the position of the delimiter
    temp = numbers_str.substr(0, pos);      //get the token
    numbers_str.erase(0, pos + 1);          //erase it from the source 
    numbers.push_back(temp);                //and put it into the array
  }

  numbers.push_back(numbers_str);           //the last token is all alone 
  std::cout << "Number " << 3 << " is " << numbers[3] << std::endl;

  return(0);
}

http://faq.cprogramming.com/cgi-bin/...&id=1044780608

There's also an example for doing something similar in C.

thanks for the FAQ link. I didn't know what a token was so I didn't open the link when i searched parse. And Thanks everyone for suggesting streamstring. I just recently switched from only using char arrays to using strings.

Sorry, one more question. Can you add a string to a stringstream that has been declared alread?

Yes, use the str() function to reset the data inside the stringstream to whatever you pass to it. If you want to add on to the existing string, it might be more complicated, although it may be as simple as using operator<<.

I was thinking of using a straight stringstream (not ostringstream or istringstream), and mixing >> and <<. I don't know if the language allows this, or if any particular compiler handles it correctly.

Code:

stringstream strStrm("Hello World Goodbye");
string firstWord;
strStrm >> firstWord;
strStrm << firstWord;
cout << strStrm.str();  // " World GoodbyeHello" ??

Don't have time to test it right now.

@ Daved : It's not that easy. To get the effect you want you have to manipulate the get and put positions of the stringstream. Reading from the stringstream does not change the contents returned by str(), but you can read from the current get-position to the end using getline().
like that

Code:

   stringstream strStrm("Hello World Goodbye");
   string firstWord;
   strStrm >> firstWord;
   strStrm.seekp(0, ios::end);
   strStrm  << firstWord;
   string manipulated;
   getline( strStrm, manipulated );
   cout << manipulated << endl;

my output:

Code:

 World GoodbyeHello

Kurt

OK, thanks. Hopefully the OP just wants to reset the stream's value, which would be much less of a hassle.