Trouble with vectors

I am writing a program to read in a line of text and then replace all four letter words with the word 'love'. I am getting the following compiler error:

love.cpp: In function ‘void replace(std::vector<char, std::allocator<char> >&)’:love.cpp:60: error: ISO C++ forbids comparison between pointer and integer

line 60 is the while statement in the replace function.

I am hoping someone could point me in the right direction. Thank you in advance.

Code:

#include <iostream>
#include <vector>

using namespace std;

void introduction();
//Explains what the program does

void get_input(vector<char>& v);
//Asks user to input text

void replace(vector<char>& v);
//Replaces all four letter words with the word love.

void output(vector<char> v);
//Outputs new sentence.

int main()
{
	vector<char> v_input;
	introduction();
	get_input(v_input);
	replace(v_input);
	output(v_input);
	return 0;
}

//uses iostream
void introduction()
{
	cout << "This program will ask the user to input a sentence and\n"
	     << "then will output the sentence with all four letter words\n"
	     << "replaced with the word 'love'\n"
	     << endl;
}

//uses iostream
//uses vector
void get_input(vector<char>& v)
{
	char tmp;
	cout << "Please type in a sentence:\n";
	cin.get(tmp);
	do
	{
		if (!cin.get(tmp))  //breaks if character is not able to be read in
			break;
		v.push_back(tmp);
	}while (tmp != '\n');
	
}		

//uses iostream
//uses vector
void replace(vector<char>& v)
{
	int j, count;
	for (int i = 0; i < v.size(); i++)
	{
		j = i + 1;

		// now checking to see if the next word is = 4 letters
		while (v[j] != '\n' || v[j] != ' ' || v[j] != '.' || v[j] != ',' || v[j] != "")
		{
			count++;
			j++;
		}
		if (count == 4)  //replaces 4 letter word with 'love'
		{
			v.push_back('l');
			v.push_back('o');
			v.push_back('v');
			v.push_back('e');
		}
		i = i + j;
	}
}

//uses iostream
//uses vector
void output(vector<char> v)
{
	cout << endl
	     << "The new sentence with the words replaced is:\n";
	for (int i = 0; i < v.size(); i++)
	{
		cout << v[i];
	}
	cout << endl;
}

Code:

while (v[j] != '\n' || v[j] != ' ' || v[j] != '.' || v[j] != ',' || v[j] != "")

a char cannot be nothing. remove that.
Kurt

Well, it could be the null character. Almost nothing.

"" is a string literal, which in C++ means it's a char*. Hence your illegal pointer comparison error. Change it to '\0' if you want to test for the null character.

Thank you, you guys are good, compiles now. I tried running it, was able to type in line of text but upon hitting return the reply was 'segmentation fault'. I put in 'cout << "1" ' in the do while loop to see if the loop iterated, which it did for about 40 times and then the segmentation fault. Do I need to declare a size for the vector?

this should do

Code:

	for (int i = 0; i-1 < v.size(); i++)

Kurt

>> i-1 < v.size();
That should be i+1 or v.size()-1. However, it will take more than that. The while loop inside the for loop could go forever. You need to check that j < v.size() before using v[j]. I would just make it the first part of the while loop and && it with the rest of the condition.

True. could also be

Code:

for (int i = 0; i < v.size()-4; i++)

othewise it can't be a 4 -letter word
Kurt

Yes, but the interior while loop still needs modification. It doesn't stop at 4 characters.

true again.
Kurt

How can you replace characters by doing push_backs?

(The whole thing would probably be simpler if you switched over to std::string, used its replace method to do the replacing, and possibly find_first_of and find_first_not_of to identify the beginning and ending of each word.)

Thank you all, I used everyone's tips. I switched from using a vector to using an array and changed the loops, now it works. I'm learnin'

>> I switched from using a vector to using an array
Really? How do you resize the array. I don't think anybody was advising that, in most cases that would be a step in the wrong direction.