7.6. A run-time error

Way back in Section 1.4.2 I talked about run-time errors, which are errors that don’t appear until a program has started running.

So far, you probably haven’t seen many run-time errors, because we haven’t been doing many things that can cause one. Well, now we are. If you use the [] operator and you provide an index that is negative or greater than length-1, you will get a run-time error and a message something like this:

index out of range: 6, string: banana

Try it in your development environment and see how it looks.

Running the active code below will result in a runtime error. Can you fix it so that we print out the first letter and last letter of string greeting instead of indexing out of range?

#include <iostream> using namespace std; int main() { string greeting = "Hello world"; cout << "The first letter is " << greeting[-1] << endl; cout << "The last letter is " << greeting[greeting.length()] << endl; }

Q-2: Click on each spot that would cause a runtime error.Remember, an index that is negative or greater than the length of the string - 1 will give a run-time error.

int main() {
    string fruit = "apple";
    char letter = fruit[0];
    char letter = fruit[9];
    cout << fruit << endl;
    cout <<  fruit[-4]  << endl;
    cout <<  fruit[4]  << endl;
}

Construct a block of code that correctly changes the string to say “cat in the hat” instead of “cat on the mat”, then print it.

        int main() {

   string sentence = "cat on the mat";

   sentence[4] = "i";

   sentence[5] = "i"; #distractor

   sentence[3] = "i"; #distractor

   sentence[11] = "h";

   sentence [12] = "h"; #distractor

   sentence[11] = "h" #distractor

   cout << sentence << endl;

}
        

You have attempted 1 of 4 activities on this page