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Chapter 18: Problem 4

(Fill in the Blanks) Fill in the blanks in each of the following: a) Class string member function \(\quad\) converts a string to a C-style string. b) Class string member function \(\quad\) is used for assignment. c) \(\quad\) is the return type of function rbegin. d) Class string member function \(\quad\) is used to retrieve a substring.

Short Answer

Expert verified
`c_str()`, `operator=`, `std::string::reverse_iterator`, `substr()`

Step by step solution

01

Identify Member Function for C-style String Conversion

To convert a `std::string` to a C-style string (character array), the member function `c_str()` is used.
02

Determine Member Function for Assignment

For assignment operations on `std::string` objects, the member function `operator=` is used.
03

Find Return Type of Function rbegin

The function `rbegin()` is used to get a reverse iterator to the beginning of the string, and its return type is `std::string::reverse_iterator`.
04

Ascertain Member Function for Retrieving Substrings

To retrieve a substring of a `std::string`, the member function `substr()` is used.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding c_str() in C++ Strings
The c_str() member function is fundamental when dealing with C++ strings, especially when you need to interact with functions that require a C-style string (null-terminated character array). You can think of this function as a bridge between the modern C++ string class and the older C-style strings.

For example, if you have a std::string named myString and you want to use a C library function that requires a C-style string, you would call myString.c_str(). This will return a pointer to an array that contains a null-terminated sequence of characters representing the current value of the std::string.
Operator= for String Assignments
Strings in C++ are objects, and objects come with special functionalities. The operator= is one such functionality that allows for an elegant and efficient way of assigning one string to another. This operator overloading ensures that you can use a natural syntax similar to primitive data types.

For instance, if you have two string objects, strOriginal and strCopy, and you wish to copy the contents of strOriginal into strCopy, a simple strCopy = strOriginal will do the trick. This operator ensures a deep copy of the string content and is designed to be safe against self-assignment.
Reverse Iterators in C++ Strings
The reverse iterator is a powerful tool to traverse a string in the reverse direction. When rbegin() is called on a std::string, it returns a std::string::reverse_iterator. This special iterator starts at the end of the string and moves backwards.

To illustrate, suppose you have a string called greeting, and you wish to iterate over it from the end to the beginning. You would use a reverse iterator as follows: 
for (auto rit = greeting.rbegin(); rit != greeting.rend(); ++rit) {    // Process *rit}
Here, rit is the reverse iterator, and you'll notice that it provides access to the characters in reverse, making certain algorithms more intuitive to implement.
Retrieving Substrings with substr()
Substring operations are a staple in text processing. The substr() function of the std::string class allows you to obtain a string that consists of a part of another string. It accepts two parameters: the starting index and the length of the substring.

Picture using substr() to get the first five characters of the string essay. You would use essay.substr(0, 5). It's an invaluable function when parsing strings, looking for patterns, or simply when you need to extract specific segments of text for further processing.

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Most popular questions from this chapter

Write a program that counts the total number of vowels in a sentence. Output the frequency of each vowel.

Some information on the Internet may be encrypted with a simple algorithm known as "rot13," which rotates each character by 13 positions in the alphabet. Thus, 'a' corresponds to 'n', and'x' corresponds to 'k'. rot13 is an example of symmetric key encryption. With symmetric key encryption, both the encrypter and decrypter use the same key. a) Write a program that encrypts a message using rot13. b) Write a program that decrypts the scrambled message using 13 as the key. c) After writing the programs of part (a) and part (b), briefly answer the following question: If you did not know the key for part (b), how difficult do you think it would be to break the code? What if you had access to substantial computing power (e.g., supercomputers)? In Exercise 18.25 we ask you to write a program to accomplish this.

Write a program that reads in several strings and prints only those ending in "r" or "ay". Only lowercase letters should be considered.

Write a program that separately inputs a first name and a last name and concatenates the two into a new string. Show two techniques for accomplishing this task.

Write a program that inputs a sentence and counts the number of palindromes in it. A palindrome is a word that reads the same backward and forward. For example, "tree" is not a palindrome, but "noon" is.
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