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Tip of the Day
Language: C
Expertise: Beginner
Aug 21, 2003

Use the Count Algorithm to Perform Simple Validation on Strings

Sometimes it's necessary to perform a simple validation on a string to ensure, for example, that a string destined to be converted to a float contains only a single '.'.

If only simple validation of some kind is required, it's trivial to use the count algorithm to tally up suspected chars and report their numbers, as in:

#include <iostream>
#include <algorithm>
#include <string>

using namespace std;

int main()

	string n = "joebob@bigtrucks@com";
	string d = "12.34";

	int A = count(n.begin(), n.end(), '@');
	int C = count(d.begin(), d.end(), '.');

	cout << "There are " << A << " @ signs in JoeBob's email address!" <<
	cout << "There's " << C << " decimal point in JoeBob's checking balance."
<< endl;

	return 0;
It's nice to remember that strings are containers in the STL, just like a vector or list, and that their iterators refer to char pointers that can be counted, sorted, or partitioned just like any other collection of values.

Greg McClure
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