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string.get(char)

Pages: 12
vince510 (55)
I am trying to take a string and grab each character from it so i can observe it. Doesn't seem to be working. Is there another way to accomplish what i am trying to do?

 
 
string.get(char)


Zhuge (4664)
Use the [] operator or .at()
vince510 (55)
I haven't learned those operators yet. Could you give an example of how they are used? Thanks.
AngelGithara23 (33)
Also, you might use a string::iterator. Here's a long winded example:
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string::iterator it;		// The string iterator.
string wordString;

for (it= wordString.begin(); it != wordString.end(); it++)
{		

  if ((*it) == '\n')							
	it = wordString.erase (it);	

  if ((*it) == '!')
	it = wordString.erase (it);

  if ((*it) == '?')
	it = wordString.erase (it);

  if ((*it) == ',')
	it = wordString.erase (it);
}

// Or . . .
for (int n = 0; n != wordString.end(); n++)
{
    cout << wordString[n] << endl;
}
Last edited on
firedraco (6243)
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string MyString("123456");
MyString.at(2); //gets '2'
MyString[2]; //also gets '2'
MyString.at(99); //gives an error
MyString[99]; //doesn't
vince510 (55)
Thanks I think that should work. I might have to create a counter to make it grab each one 1by1 where i thought if i put the string.get(char) in a loop i would be able to grab it in each iteration.
vince510 (55)
Okay so i'm confused now. Heres what I am trying to do. I need to take roman numerals and convert them into a decimal number.

I was thinking about using the MyString.at() function... But I need to assign it to a character, so i dont think that will work. Unless I can say char = 'MyString.at()' or something like that.
Last edited on
vince510 (55)
i used the .at function and now its crashing with a runtime error. Can someone explain why this is happening/


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void convertNumeral(/*in*/ string numeral,
		            /*out*/ int& decimal)

{

	char singleNumeral;
	int iterateCount;

	singleNumeral = numeral.at(iterateCount);
	
    while(singleNumeral != ' ')
    {
                        
		if(singleNumeral == 'M')
			decimal = decimal + 1000;
		if(singleNumeral == 'D')
			decimal = decimal + 500;
		if(singleNumeral == 'C')
			decimal = decimal + 100;
		if(singleNumeral == 'L')
			decimal = decimal + 50;
		if(singleNumeral == 'X')
			decimal = decimal + 10;
		if(singleNumeral == 'V')
			decimal = decimal + 5;
		if(singleNumeral == 'I')
			decimal = decimal + 1;
		
        iterateCount++;	
		singleNumeral = numeral.at(iterateCount);

	}
	
}
firedraco (6243)
You never initialize iterateCount, so it is some random unknown value that is probably not what you want.
vince510 (55)
I will try that. Thanks. The .at function worked perfect.
vince510 (55)
Still getting the runtime error. I just assumed the itearateCount was working because when i ran it with a test cout, it output the correct character.
AngelGithara23 (33)
Maybe it will work better like this; its just a guess . . .
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string numeral;
int iterateCount = 0;
string::iterator it;	

for (it= numeral.begin(); it != numeral.end(); it++)
{	
  if ((*it) == ' ')	
     it = numeral.end();

  if ((*it) == 'M')							
	decimal = decimal + 1000;

  singleNumeral = numeral [iterateCount]; 
  iterateCount++;	
}


I know I use the for loop probably too often but maybe this will help. I am a beginner so there's a better way, but I want you to find your solution or at least something that works.
Good luck.
Last edited on
vince510 (55)
Thanks for the possible solution angelGithara23, but i dont understand the 'for' loop or string iterator at the moment. i've grasped the while loop and would like to use it and not jump to functions that i don't understand or haven't gotten to. If you can come up with a solution with a while() loop, i would love to see it.
Last edited on
firedraco (6243)
Make sure you are not going out of bounds on the vector...If you have the new code I could check that too.

@Angel: That would work fine, and you wouldn't need singleNumber or interateCount in that case actually.
Last edited on
AngelGithara23 (33)
@ vince: well, If you are uneducated on the language, with all respect, vince, I would hope that you would learn more about control structures before jumping into a more complicated thing like functions, because control structures are a logical constituent of functions. 
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#include <iostream>
#include <string>
using namespace std;

int main ()
{
	int decimal = 0;
	string numeral = "IV", stringTemp = ""; 
	int iterateCount = 0;
	string::iterator it;	

	for (it= numeral.begin(); it != numeral.end(); it++)
	{	
	  iterateCount++;

	  if ((*it) == ' ')	
		  it = numeral.end();
	  else  
		  stringTemp = stringTemp + *it;	
	  
	  if (iterateCount == 2)
	  {
	     if(stringTemp == "IV")
		    decimal = 4;
	  }
	  else if(stringTemp == "V")
			decimal = decimal + 5;
	  else if(stringTemp == "I")
			decimal = decimal + 1;
	 	
	}

	cout << decimal;

	cin.get();
	return 0;
}

Here this should work once you have studied for loops a little, and look at the easy to use STL reference at this excellent site to learn more about the useful string::iterator. And if you have difficulties figuring out the rest just ask more questions (or PM me) and I'll try to help figure some of that out with you.

@ firedraco: Are you saying I can get a int count from a string::iterator? How? That would actually help me to know that. Oh, I get what you're saying now, duh.
Last edited on
firedraco (6243)
You can't, it's just you don't need to have those other variables. (*it) will give you whatever it is pointing at without needing to have an int index;.
vince510 (55)
I cant figure it out. please take a look and try my existing code and help debug it i would appreciate it. I think it has to do with the (singleNumeral != ' ') loop with the string. it seems to get 2 good iterations with a 3 character roman numeral and crashes...

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//Roman Numeral Calculator
// vincent 

#include <iostream>
#include <cstdlib>

using namespace std;

void convertNumeral( string, int&);
void convertDecimalPrint(int);
void calculateSum(int, char, int, int&);

int main()
{
    string numeral, numeral1, numeral2;
    int value1, value2, decimalValue, decimalSum;
    char arithmetic;
    
    cout << "This program will calculate 2 roman numeral numbers" << endl
         << "and print out the decimal values and sum in roman numerals." << endl << endl;
    cout << "Input first roman numeral number: ";
    cin >> numeral;
    cout << endl << numeral;
    
    numeral1 = numeral;
    
    convertNumeral(numeral, decimalValue);
    
    cout << "test";
    
    value1 = decimalValue; 
    
    cout << endl << "The first number is " << value1 << endl;
    
    cout << "Input second roman numeral number: ";
    cin >> numeral;
    cout << endl << numeral;
    
    numeral2 = numeral;
    
    convertNumeral(numeral, decimalValue);
    
    value2 = decimalValue;
    
    cout << endl << "The second number is " << value2 << endl;
    
    cout << "Enter the desired arithmetic operation : ";
    cin >> arithmetic;
    cout << endl << arithmetic;
    
    calculateSum(value1, arithmetic, value2, decimalSum);
    
    cout << numeral1 << " " << arithmetic << " " << numeral2 << " = ";
    
    convertDecimalPrint(decimalSum);
    
    cout << " (" << decimalSum << ")";
    
    system("pause");
    return 0;
    
}
    
    
    
//**************************************************************************
// convert numeral to decimal number


void convertNumeral(/*in*/ string numeral,
		            /*out*/ int& decimal)

{

	char singleNumeral;
	int iterateCount;
	
	iterateCount = 0; //  integer to make .at function go to next character
	decimal = 0;

	singleNumeral = numeral.at(iterateCount);
	
    while(singleNumeral != ' ')
    {
        cout << decimal;
        cout << singleNumeral;               
		if(singleNumeral == 'M')
			decimal = decimal + 1000;
		if(singleNumeral == 'D')
			decimal = decimal + 500;
		if(singleNumeral == 'C')
			decimal = decimal + 100;
		if(singleNumeral == 'L')
			decimal = decimal + 50;
		if(singleNumeral == 'X')
			decimal = decimal + 10;
		if(singleNumeral == 'V')
			decimal = decimal + 5;
		if(singleNumeral == 'I')
			decimal = decimal + 1;
		
        iterateCount++;	
		singleNumeral = numeral.at(iterateCount);
        cout << decimal;
	}
	
}
    


//***************************************************************************
// convert decimal number to numeral (prints out)

void convertDecimalPrint(/*in*/ int decimalSum)
{
	while(decimalSum >= 1000)
		{
		cout << "M";
		decimalSum = decimalSum - 1000;
		}
	while(decimalSum >= 500)
		{
		cout << "D";
		decimalSum = decimalSum - 500;
		}
	while(decimalSum >= 100)
		{
		cout << "C";
		decimalSum = decimalSum - 100;
		}
	while(decimalSum >= 50)
		{
		cout << "L";
		decimalSum = decimalSum - 50;
		}
	while(decimalSum >= 10)
		{
		cout << "X";
		decimalSum = decimalSum - 10;
		}
	while(decimalSum >= 5)
		{
		cout << "V";
		decimalSum = decimalSum - 5;
		}
	while(decimalSum >= 1)
		{
		cout << "I";
		decimalSum = decimalSum - 1;
		}
		
}
		
//*****************************************************************************
// calculate the numbers

void calculateSum(int value1,
                  char arithmetic,
                  int value2,
                  int& decimalSum)
                          
{
                          if(arithmetic == '+')
                          decimalSum = value1 + value2;
                          if(arithmetic == '-')
                          decimalSum = value1 - value2;
                          if(arithmetic == '*')
                          decimalSum = value1 * value2;
                          if(arithmetic == '/')
                          decimalSum = value1 / value2;
}
Last edited on
firedraco (6243)
I see the problem. If you simply type in something like "XI" then hit the Enter key, there is no space. In this case I would suggest using getline() the get the data, then iterating over the string with respect to it's size as opposed to whether you find a space.

For getline():
http://www.cplusplus.com/forum/articles/6046/
vince510 (55)
I dont want to sound naive or doubtful about getline(), but assuming that a user doesn't know that they have to input a following space with getline() and they just input a standard roman numeral without a following space. wouldn't it still do the same thing as cin? maybe concatenate a space onto the user input?
vince510 (55)
It worked! concatenating the numeral variable with numeral = numeral + " "; worked. Thanks for the help guys!
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