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Tip of the Day
Language: C++
Expertise: Beginner
Oct 17, 2006



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Range Checking Vectors

This standard library vector can be used like an array. For example:

std::vector v(2); // vector of size 2
v[0] = 5;
v[1] = v[0];
If you're using an out-of-range index, the behavior is undefined. The program might crash without an appropriate error message. The statement:

v[2] = 0;
gives undefined behavior. To access a vector element safely, the at() member function may be used rather than the operator[]. While the statements:

v.at(0) = 5;
v.at(1) = v.at(0);
have the same effects as the statements indicated in the example above, the statement:

v.at(2) = 0;
does not cause undefined behavior, instead it throws an std::out_of_range exception.

Kevin Spiteri
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