deleting parts of a string

This is a discussion on deleting parts of a string within the C++ Programming forums, part of the General Programming Boards category; I'm trying to get my program to go through the string typed in by the user and strip it of ...

  1. #1
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    Red face deleting parts of a string

    I'm trying to get my program to go through the string typed in by the user and strip it of EVERYTHING but the numbers. I can't place my finger on what I'm missing. Help please?

    Code:
    #include<iostream>
    #include<string>
    using namespace std ;
    
    int main()
    {
    	string myString ;
    
    	cout << "Please enter string/numbers: " ;
    	
    	getline( cin, myString ) ;
    
    	// disgard anything that's not an int
    	for ( int x = 0 ; x < 10 ; x++ )
    	if ( !isdigit( myString[ x ] ) )
    		myString.erase( x, 1 ) ;
    
    	// display contents
    	cout << myString << endl ;
    } // end main

  2. #2
    Registered User jdragyn's Avatar
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    Are you sure every string that a user types in is going to be exactly 10 characters long?
    C+/- programmer extraordinaire

  3. #3
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    That's another thing... when I make the number greater than 10 (say 15) I get an error when I try to enter anything into the program at runtime...

  4. #4
    Registered User jdragyn's Avatar
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    Well, aside from needing to use the .length() operator (or another method entirely), what exactly is it not doing that you need it to do?
    C+/- programmer extraordinaire

  5. #5
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    Hmmm... I tried the .length as you suggested, but still get the runtime error... I'm trying to make sure that the user doesn't enter any data other than numbers.

    Code:
    #include<iostream>
    #include<string>
    using namespace std ;
    
    int main()
    {
    	string myString ;
    
    	cout << "Please enter string/numbers: " ;
    	
    	getline( cin, myString ) ;
    
    	// disgard anything that's not an int
    	for ( int x = 0 ; myString.length() ; x++ )
    	if ( !isdigit( myString[ x ] ) )
    		myString.erase( x, 1 ) ;
    
    	// display contents
    	cout << myString << endl ;
    } // end main

  6. #6
    Registered User jdragyn's Avatar
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    What do you think happens to the string when you erase a character from it?
    C+/- programmer extraordinaire

  7. #7
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    sounds to me like you need to create a way to block all input except numbers from being entered, have you tried using a
    Code:
    if(cin.fail==1){}
    which will trigger if any letter is used to represent a number (such as typing "seven" instead of "7")?

    another possible option would be to to use the pop_back() function, however u would have to swap the value u want to get rid of with the last value, then resort, if the list was sorted
    Last edited by Creatlv3; 05-07-2010 at 07:48 PM.

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