cstring

This is a discussion on cstring within the C++ Programming forums, part of the General Programming Boards category; i have a string that has various sized spaces between the words, (e.g the big brown fox jumps over the ...

  1. #1
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    cstring

    i have a string that has various sized spaces between the words, (e.g the big brown fox jumps over the fence.)
    i am trying to assign each of the words to an array and then rejoin the array of words without the spaces. is this easy?
    i have also been advised to use strcmp. but i am not sure how this would work.

    help would be great.

  2. #2
    C++ Witch laserlight's Avatar
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    Pretty easy using string streams. You would not even need an array as you can join the words back by concatenating to the result string.
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  3. #3
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    is this easy?
    That's up to you to decide:
    Code:
    const char* cstr = "hello    world goodbye  world";
    
    string str(cstr);  //cstring-->c++ string
    istringstream input(str); //creates a container called 'input', which 
    	                   //you can read from like a file
    
    string result="";
    string current = "";
    
    while(input>>current)  //read from input as if it were a file
    {                       //the >> operator skips leading whitespace until it finds a character, 
                             //then it stops reading as soon as it encounters trailing whitespace
    
    	result += current;
    }
    
    cout<<result<<endl;  //helloworldgoodbyeworld
    Last edited by 7stud; 01-23-2007 at 05:14 AM.

  4. #4
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    ok. that makes sense. here is my code so far. i am missing something pretty basic.
    Code:
    #include <iostream>
    #include <fstream>
    #include <string>
    
    using std::cout;
    using std::endl;
    using std::cerr;
    using std::string;
    using std::getline;
    
    int main ()
    {
      string myStringErrors;
    
      std::ifstream file("Lab1.txt");
      
      if (!file)
        {
        cerr<<"Can't open file"<<endl;
        return EXIT_FAILURE;
        }
     //read file one line at a time
      while (std::getline(file,myStringErrors))
        {
        //do stuff with line
        cout<<myStringErrors<<endl;
    
    	const char* myStringNoSpaces = myStringErrors;
    
    	string str(myStringNoSpaces);		//cstring-->c++ string
    	istringstream input(str);			//creates a container called 'input', which
    										//you can read from like a file
    	string result="";
    	string current = "";
    
    	while(input>>current)				//read from input as if it were a file
    	{									//the >> operator skips leading whitespace
    	result += current;
    	}
    
    	cout<<result<<endl;
    	}
       cout<<endl;
    }
    when i compile i always get an error message saying : cannot convert from 'std::string' to 'const char *'. how do i change my std::string? can i change my std::string to suit?

  5. #5
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    Whenever you ask a question about an error, ALWAYS post a message on the line that has the error, like this:
    Code:
    int n = 10.5;  //***ERROR***
    Or, post the error message along with the line of code:
    error message saying : cannot convert from 'std::string' to 'const char *'.
    which is this line of code:

    int n = 10.5;
    You can't assign a string type to a variable that is of type const char*. This code makes no sense:
    Code:
    string myStringErrors;
    ...
    const char* myStringNoSpaces = myStringErrors;
    string str(myStringNoSpaces)
    You try to convert myStringErrors from a string type to a const char*. Then you convert the result back to a string type. Hello? You had a string type to start with.
    Last edited by 7stud; 01-23-2007 at 05:39 AM.

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    as i am sure you can tell i am new to programming and it is definately not my strong point. i was told that to eliminate spaces i should use 'strcmp' (not sure how that is going to help) or to assign my string to an array. the string 'myStringErrors' is from a file that was given to me. this i managed to open after hours of trying. but once opend i was told to assign each individual word to an array and then rejoin the array without the spaces. i have been sitting for hours doing this. no luck. also thought that maybe 'strcpy' with a loop using string::replace (' ', ' ') will any of these work or am i wasting my time?

    thank you for the tips on error message posting. much appreciated

  7. #7
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    Well suppose your code did this:

    int num = 10;
    int irrelevant = num;
    num = irrelevant;

    What would you do to make that code more efficient?

  8. #8
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    not sure. sorry. do you need both variables? if not: int num = 10;.

  9. #9
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    Ok, now apply that same logic to this code:
    Code:
    string myStringErrors;
    ...
    std::getline(file,myStringErrors)
    ...
    const char* myStringNoSpaces = myStringErrors;
    string str(myStringNoSpaces);
    istringstream input(str);

  10. #10
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    sorry. get what you mean now. will have a look. this is frustrationg me now. need a break i think.

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