1. Object Oriented Programming COP3330 / CGS5409
Recitation Week 10
Object Oriented Programming
COP3330 / CGS5409

2. Today’s Recitation c-strings vs. concept of string class
Dynamic review
Assignment 5

3. C-style strings
Recall that a C-string is implemented as a null-terminated array of type char
No built-in string type in C. Must use character arrays
NOT every character array is a C-string. Only when terminated with the null-character
String literals in code ("Hello World", "John Smith") are implemented as constant C- strings

4. The <cstring> library
Contains functions for common string operations, such as copy, compare, concatenate, length, search, tokenization, and more
strlen() strcpy(), strncpy() strcat(), strncat() strcmp(), strncmp() strstr() strtok() etc.

5. Special features in <iostream>
Special built-in functions for I/O handling of C-style strings, like the insertion and extraction operators, get(), getline(), etc
char str1[40];
cout << str1; // insertion operator for strings
cin >> str1; // extraction, reads up to white space
cin.get(str1, 40, ','); // reads to delimeter (comma)
cin.getline(sr1, 40); // reads to delimiter (default delimiter
// is newline), discards delimiter

6. The DOWN side of C-strings
Fixed length, when declared as a normal C-style array This is fine for things like database fields, where a fixed size on each field is necessary
Not so flexible for storing just any old string.
string name really just acts as a pointer, since it's the name of an array As such, always must be passed in and out of functions by address -- i.e. with pointer parameter type or return type
Must be careful of array boundaries. Overflow of string boundary not automatically detected Less intuitive function calls for common operations, like comparison or copying:

7. The DOWN side of C-strings
// Consider: I want to assign "Hello World" to a string called greeting: char greeting[40]; // can I now say the following? (Which would be pretty intuitive) greeting = "Hello World"; // Legal? NO! // Instead, I have to do it this way, with the strcpy function: strcpy(greeting, "Hello World"); // Comparison: This call doesn't compare contents, only pointers: if (str1 == str2) // For c-strings, use strcmp: if (strcmp(str1, str2) == 0) // then strings are the same

8. Building a String class
Use dynamic allocation and resizing to get flexible capacity
Do all dynamic memory management inside the class, so the user of string objects doesn't have to!
Use operator overloads if more intuitive notations are desired
insertion, extraction operators for easy I/O
comparison operators for easy comparisons, sorting, etc.
operator+ for concatenation, if desired
Build copy constructor and assignment operator to for correct assignment and pass-by-value abilities
Build a conversion constructor to convert c-style strings to string objects, for automatic type conversions!
Could include conversion constructors for converting other types to strings, too

9. example String class
BString class

10. Assignment 5 intro/issues
Don't wait until the last minute to start this one!!!
Use good principles like we did in the BString example (and other DMA examples)
separate out the memory management functions from the algorithmic features.
This means, avoid doing TONS of "new" and "delete" calls everywhere -- restrict those to a select set of functions. This will make your life easier as you code this
Decide on storage first, and then make sure all of your functions adhere to whatever rules you set up in advance for your storage

11. Questions?