Note 7.3.1.
In C++, indexing begins at 0!
Section 7.3 Extracting characters from a string
Strings are called “strings” because they are made up of a sequence, or string, of characters. The first operation we are going to perform on a string is to extract one of the characters. C++ uses square brackets (
[ and ]) for this operation.
fruit using [ and ].The expression
fruit[1] indicates that I want character number 1 from the string named fruit. The result is stored in a char named letter. When I output the value of letter, I get a surprise:
a
a is not the first letter of "banana". Unless you are a computer scientist. For perverse reasons, computer scientists always start counting from zero. The 0th letter (“zeroeth”) of "banana" is b. The 1th letter (“oneth”) is a and the 2th (“twoeth”) letter is n .
If you want the the zereoth letter of a string, you have to put zero in the square brackets.
fruit.Checkpoint 7.3.1.
What would replace the “?” in order to access the letter “b” in the string below?
#include <iostream>
using namespace std;
int main() {
string bake = "bake a cake!";
char letter = bake[?];
}
- 1
- Don’t forget that computer scientists do not start counting at 1!
- 0
- Yes, this would access the letter "b".
- 2
- This would access the letter "k".
Checkpoint 7.3.2.
What is printed when the code below is run?
#include <iostream>
using namespace std;
int main() {
string lunch = "hello";
string person = "deejay";
lunch[0] = lunch[3];
cout << lunch;
}
- lunch
- When we
coutastringwe print its content not its name. - jello
- Carefully check which string(s) we are indexing into.
- lello
- Correct! We copy the ’l’ from position 3 of "hello" to position 0.
- heljo
- Consider which string(s) we are indexing into.
Checkpoint 7.3.3.
Checkpoint 7.3.4.
Construct a block of code that correctly prints the letter “a”.
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