Programming Forums > Application Development > C++

357mag · Jun 14th, 2007, 8:19 PM

This probably is going to be just one of several questions I'm going to ask regarding this program. The program has a string of text, and then replaces a word with another word. But to start with all I'm trying to do here is just output the index positions of the word "rose". Here is the program:

(Toggle Plain Text)

int main()
{
	string text = "A rose is just a rose is a rose.";
	string word = "rose";
	string replacement = "thorn";

	int start = text.find(word);

	cout << start << endl;

	while (start != string::npos)
	{
		text.replace(start, word.length(), replacement);
		start = text.find(word);
		cout << start << endl;
    }

	return 0;
}

When I run the program it outputs the following:

2
18
29
-1

But I was expecting it to output the following:

2
17
27

Because the index position of the first occurrence of the word "rose" is found at index position 2. Then if you keep counting, the second occurrence of the word "rose" is found at index postion 17. And the final occurrence of the word "rose" is found at index position 27. And I don't know what the -1 is for either(maybe that is the illegal character position that is returned when the while test condition eventually fails).

DaWei · Jun 14th, 2007, 8:25 PM

Surely you realize that if the word, "rose", is replaced by the word, "thorn", then every subsequent character moves to a position one greater than before. Your next find operation works on the NEW text, not the old text.

Incidentally, have you checked on the value of string::npos in your environment?

Jun 14th, 2007, 8:19 PM	#1
357mag Hobbyist Programmer Join Date: Mar 2005 Posts: 148 Rep Power: 4	Replacing a word with another word This probably is going to be just one of several questions I'm going to ask regarding this program. The program has a string of text, and then replaces a word with another word. But to start with all I'm trying to do here is just output the index positions of the word "rose". Here is the program: (Toggle Plain Text) int main() { string text = "A rose is just a rose is a rose."; string word = "rose"; string replacement = "thorn"; int start = text.find(word); cout << start << endl; while (start != string::npos) { text.replace(start, word.length(), replacement); start = text.find(word); cout << start << endl; } return 0; } int main() { string text = "A rose is just a rose is a rose."; string word = "rose"; string replacement = "thorn"; int start = text.find(word); cout << start << endl; while (start != string::npos) { text.replace(start, word.length(), replacement); start = text.find(word); cout << start << endl; } return 0; } When I run the program it outputs the following: 2 18 29 -1 But I was expecting it to output the following: 2 17 27 Because the index position of the first occurrence of the word "rose" is found at index position 2. Then if you keep counting, the second occurrence of the word "rose" is found at index postion 17. And the final occurrence of the word "rose" is found at index position 27. And I don't know what the -1 is for either(maybe that is the illegal character position that is returned when the while test condition eventually fails).

Jun 14th, 2007, 8:25 PM	#2
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Surely you realize that if the word, "rose", is replaced by the word, "thorn", then every subsequent character moves to a position one greater than before. Your next find operation works on the NEW text, not the old text. Incidentally, have you checked on the value of string::npos in your environment? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > C++

Replacing a word with another word