Chapter 10 - Characters, C-Strings, and More About the string Class

Character Testing

• requires <cctype> header file

Character Case Conversion

• toupper

  • if char argument is lowercase letter, return the ASCII code for the uppercase equivalent; otherwise, return the argument’s ASCII code unchanged

  • if you want to send the returned value to cout, use a cast expression to display it as a character

    • cout << static_cast<char>toupper(char1);

• tolower

  • if char argument is uppercase letter, return the ASCII code for its lowercase equivalent; otherwise, return the argument’s ASCII code unchanged

  • use case expression for cout

C-Strings

• C-String: sequence of characters stored in adjacent memory locations and terminated by NULL character

• String literal (string constant): sequence of characters enclosed in double quotes “ “

  • ex: “Hi there!“

• an array of chars can be used to define storage for a string

  • leave room for NULL at the end

  • can enter a value using cin or >>

    • input is whitespace-terminated

    • no check to see if there’s enough space

  • for input containing whitespace, and to control amount of input, use cin.getline()

Display Contents of Character Array

Library Functions for Working with C-Strings

• <cstring> header file

• functions take one or more C-strings as arguments:

  • C-string name

  • pointer to C-string

  • literal string

• strlen(str)

  • returns length of C-string str

• strcat(str1, str2)

  • appends str2 to the end of str1

• strcpy(str1, str2)

  • copies str2 to str1

• note: strcat and strcpy perform no bounds checking

• strstr(str1, str2)

  • finds the first occurernce of str2 in str1, returns a match, or NULL if no match

C-String/Numeric Conversion Functions

• <cstdlib> header file

• if C-string contains non-digits, results are undefined

  • function may return result up to non-digit

  • function may return 0

• itoa does no bounds checking

string to Number Conversion

The to_string Function

Writing Your Own C-String Handling Functions

• can pass arrays or pointers to char arrays

• can perform bounds checking to ensure enough space for results

• can anticipate unexpected user input

• see examples: stringCopy() & nameSlice()

The C++ string Class

• special data type that supports working with strings

  • #include <string>

• can define string variables in programs

• can receive values with assignment operator

• can be displayed via cout

• use cin

• use getline to put a line of input (spaces) into a string

• can use relational operators directly to compare string objects

  • performed similar to strcmp

Other Definitions of C++ strings

Using auto To Define a string Object

auto str = "Hello World!";

• defines str as either const char * or const char[12]

• when using auto, append the s suffix to the string literal

  • auto str = "Hello World!"s;

  • defines str as a string object

string operators

string Member Functions

• behind many overloaded operators

• assignment

  • assign, copy, data

• modification

  • append, clear, erase, insert, replace, swap

• space management

  • capacity, empty, length, resize, size

• substrings

  • find, front, back, at, substr

• comparison

  • compare

• see Table 10-9 string Class Member Functions