Introduction to C++ for Those Somewhat Familiar with C
•
3 j'aime•859 vues
Used in a bonus session for a C programming class
Recommandé
Contenu connexe
Similaire à Introduction to C++ for Those Somewhat Familiar with C
Similaire à Introduction to C++ for Those Somewhat Familiar with C (20)
Plus de Jong Wook Kim
Plus de Jong Wook Kim (7)
Dernier
Dernier (20)
Introduction to C++ for Those Somewhat Familiar with C
- 4. Background: History of C ◦ In 1970, Bell Labs needed to port Unix from PDP-7 to PDP-11 ◦ Unix, the OS, was written in assembly until those days ◦ The developers wanted to use a language, but there was no suitable one ◦ So Ritchie made one and named it C in 1972, and wrote K&R C book in 1978 ◦ The language feature has been largely fixed since then ◦ C became the language of choice for system programming ◦ People made OS using C (DOS → Windows, BSD → MacOS → iOS, Linux → Android) ◦ Because it is so simple and old, it is so fast Ken Thompson and Dennis Ritchie PDP-7 (1965) PDP-11 (1970) K&R C (1978)
- 5. But C Hasn’t Changed for Decades! “Software Crisis” became a thing circa 1970-1980 ◦ Governments and companies worked on large software projects for the first time ◦ Stock exchange, Healthcare, Combat support system, Criminal intelligence, etc. ◦ But realized: building large-scale software is totally different from building hardware ◦ Projects running over-budget and over-time ◦ Software being very inefficient and of low quality ◦ Code difficult to maintain (= spaghetti code) ◦ Projects being unmanageable To overcome the crisis, new methodologies and paradigms emerged ◦ Software Development Process / Project Management ◦ Version Control System ◦ Software Quality ◦ Birth of “Software Engineering” as a discipline
- 6. Programming Paradigms C follows imperative, procedural, and structured programming paradigm ◦ Write commands sequentially and organize them in procedures ◦ Organize associated data in structures After the crisis, programmers wanted new features and paradigms ◦ To become more productive in programming, especially in collaboration ◦ To make more robust/efficient programs ◦ To easily develop on new platforms (web, mobile) ◦ Object-Oriented Programming was the most demanded paradigm C is fixed in features and paradigms, so people created more languages ◦ C++ (’83), ObjC (’84), Python (’91), Lua (’93), Java (’95), Ruby (’95), Scala (’04), Swift (’14)
- 7. Object-Oriented Programming A paradigm that designs computer programs based on “objects” ◦ Contains structured data (in fields) and associated behaviors (in methods) ◦ OOP designs a program in terms of objects interacting with one another ◦ Keywords: abstraction, encapsulation, inheritance, polymorphism Class ◦ A popular way for a programming language to implement OOP ◦ Class: specifies the data format and available procedures, like a blueprint ◦ Instance: a realization of a class, with specific data (=state). ◦ What can be fields and methods of: Car, Person, Animal, and Radio? C++ was originally called “C with Classes” ◦ Class = struct with associated methods ◦ More on the specific syntax later
- 8. Examples class Radio - frequency: Float - volume: Float - playing: Bool - tuner: Tuner - tune(frequency: Float) - set_volume(volume: Float) - play() - stop()
- 9. Examples class Radio - playing: Bool - tuner: Tuner - volume: Float - play() - stop() - tune(frequency: Float) - set_volume(volume: Float) class Tuner circuit: Circuit tune(frequency: Float) get_audio(): Audio class Circuit anthenna: Anthenna variable_resistor: Resistor set_resistance(ohm: Float) …
- 10. Examples class Mammal - birthday: Date - weight: Float - breathe() - eat(food: Food) class Person - name: String - study() - work() class Dog - name: String - bark() - howl() class Cat - name: String - purr() - meow()
- 11. Software Design Patterns Reusable “pattern” of OOP design that can be used in many situations Provides a solution to commonly occurring problems in software design Ways of organizing relations between objects in order to: ◦ Make the program easy to read and maintain ◦ Implement wanted features efficiently ◦ Maximize reusability of the code Out of the scope of this class ◦ But a must-read for all software engineers ◦ One of them will be covered later (iterator pattern)
- 12. C++ as a Modernization of C Created by Bjarne Stroustrup in 1983, ideas originating from his PhD thesis ◦ Support Object-Oriented Programming for large-scale software development ◦ Have to be fast in speed, to be used for practical purposes ◦ Mostly a superset of C, because general-purpose, fast, portable, and widely used Philosophy ◦ Driven by real-world problems and should be useful immediately ◦ User-create types need to have the same performance as built-in types ◦ Should fully support any programming style that programmers want ◦ Allowing a useful feature is more important than preventing misuse of it C++ actively adds support for new features and paradigms ◦ While C remains an almost unchanging, minimal, portable, and efficient toolset ◦ A new Draft International Standard in March 2017, to become C++17
- 13. Timeline of C++ 1979: Stroustrup starts to work on “C with Classes” in Bell Labs 1983: Renamed to “C++” 1985: The first edition of <The C++ Programming Language> 1989: C++ 2.0 release 1998: The first ISO Standard (C++98) 2003: C++03, bugfixes of C++98 2011: C++11, a major revision 2014: C++14, bugfixes and small improvements on C++11 2017: (planned) C++17, the upcoming major revision
- 14. C++ was such a hit Date Estimated Number of Users Oct 1985 500 Oct 1986 2,000 Oct 1987 4,000 Oct 1988 15,000 Oct 1989 50,000 Oct 1990 150,000 Oct 1991 400,000 ◦ Doubled every 7.5 months in 1979-1991 ◦ More than 3 million in 2004
- 15. What Makes It So Unique The only language that: ◦ Supports modern programming paradigms necessary for large-scale development ◦ Supports straightforward and zero-overhead integration with C programs and the OS ◦ Still maintains close-to-metal performance ◦ (Feasible alternatives came up only very recently, like Rust, Go, Swift) Many performance-critical large-scale applications are built in C++ ◦ Windows, MacOS, Android, iOS, and many Linux distributions ◦ Almost all major PC/console games ◦ Almost all browsers: Google Chrome, Safari, Internet Explorer, Edge, Firefox ◦ Almost all Adobe products: Photoshop, Illustrator, Premiere, Acrobat ◦ Almost all DAW software: Logic Pro, Pro Tools, Adobe Audition, Ableton Live ◦ All major C/C++ compilers: GCC, Visual C++, Clang ◦ Core of many deep learning libraries: Tensorflow, Caffe, MXNet
- 17. Hello World ◦ C++ Headers are without the .h extension ◦ using namespace std; ◦ A namespace that contains all features of the C++ standard library ◦ No need to prefix functions with library names ◦ <iostream> provides console input/output via cin and cout ◦ Also endl, which outputs a newline and flushes the stream ◦ No need to use the format string ◦ The shift operator << has a different meaning here – Operator Overloading
- 18. Namespaces ◦ Either write using namespace std; or use the prefix std:: ◦ Can be nested to multiple depths ◦ Helps organizing functions, variables, and classes
- 20. std::string ◦ Is a “class” provided by the C++ Standard Library ◦ Start by assigning a string literal to a string variable, or in C++14, "hello"s ◦ A lot safer than the C way, manipulating strings only in char*
- 22. New & Delete ◦ C version: relies on library functions ◦ Size calculation ◦ Allocation with malloc() ◦ Type casting ◦ Initialization ◦ Deallocation with free() ◦ C++ version: a language feature ◦ All of the first 4 in one line ◦ Deallocation with delete
- 23. New [] & Delete [] ◦ Again, no need to calculate size and typecast manually ◦ new [] and delete[] have to match
- 24. Templates ◦ Template functions and template classes are “realized” according to types ◦ One implementation for many types, improving reusability of code ◦ For example: linked list of type T, hash map from type K to V
- 25. References ◦ Acts like a pointer, looks like a variable ◦ Avoids pointer insanity (to some degree) ◦ Cannot be NULL, which is a good thing ◦ Necessary for using some C++ features that we will not go into detail ◦ Operator overloading, copy constructor, move constructor
- 26. Exception Handling Most C functions use a special return value to indicate an error ◦ -1, errno, etc., usually a number ◦ Inconsistent codes per function ◦ Cannot return other types C++ encourages using exceptions ◦ Throw any variable anywhere ◦ Across function calls ◦ Catch according to the type ◦ Return value can be result type ◦ Fail-fast on the first error Controversy exists on using them
- 27. C++11: Lambdas ◦ A function can be created and passed to another function ◦ Cleaner than using function pointers ◦ Higher-order Function: a function that accepts a function(s) as its parameters ◦ An element of “Functional Programming” paradigm
- 29. More Non-OOP Features No Need to typedef struct Single-line comments using // Boolean type bool is a built-in type ◦ no need to include stdbool.h Default arguments: ◦ void foo(int a = 3) { ... Inline functions ◦ Compiler puts the content in the caller, not making a function actually nullptr instead of NULL which is just 0 ◦ Which is number, not a pointer, thus confusing and dangerous
- 32. Reminder: Object-Oriented Programming A paradigm that designs computer programs based on “objects” ◦ Contains structured data (in fields) and associated behaviors (in methods) ◦ OOP designs a program in terms of objects interacting with one another ◦ Keywords: abstraction, encapsulation, inheritance, polymorphism Class ◦ A popular way for a programming language to implement OOP ◦ Class: specifies the data format and available procedures, like a blueprint ◦ Instance: a realization of a class, with specific data (=state). C++ was originally called “C with Classes” ◦ Class = struct with associated methods ◦ More on the specific syntax later
- 33. Class = Data + Behaviors = Struct + methods Methods can be added to a struct ◦ Also known as member functions ◦ Should be associated with the struct’s data ◦ Therefore the task is a “duty” of this class ◦ Yes, A struct with methods is now a class
- 35. Constructor In the previous example, the initialization of Person’s fields was done in main() ◦ But organizing its fields should be Person’s duty Constructor does that job ◦ Called only as soon as the instance is created ◦ Parameters = any data required for initialization There can be more than one constructors ◦ One of them must be called, otherwise compile fails Can be called during declaration ◦ auto p = new Person(“Doe”) also works
- 36. An Even Better Constructor Passes the argument to the string name’s constructor. ◦ Which initializes the string class with the given argument ◦ The no-agrument constructor of string name is never called. In main(), Person is reused ◦ Providing an abstraction ◦ By grouping data (name) and behavior (printing name) inside an object.
- 38. Encapsulation: accessor Accessor (or getter) method ◦ Simply returns a field ◦ Allows others to see the value ◦ But not mutate the value ◦ Read-only for others, full access for self Abstraction to users of the class Person ◦ Only need to know ◦ The methods and constructors of the class ◦ No need to know ◦ Any private fields or methods
- 39. struct vs class The only difference is the default access level ◦ Members of struct are public by default ◦ Members of class are private by default In C, struct was just a data bundle ◦ That can be manipulated from anywhere C++ added methods to struct for class ◦ struct members have to be public by default ◦ To retain compatibility with C ◦ But C++ liked encapsulation so much! ◦ So they made class members private by default Rule of thumb ◦ Use struct for simple data storage ◦ May have minimal logic on data validation, etc. ◦ Use class for anything more than that
- 40. Inheritance – Basics Derived class inherits base class ◦ Student = Derived, Person = Base ◦ Derived class has all members of Base Makes it easier to ◦ Reuse the functionality of the base class
- 41. Inheritance – Pet Example talk() inherited to Dog and Cat: sound() overridden in Dog and Cat If base class has a constructor ◦ Must call when constructing derived ◦ Unless base constructor is zero-argument Use virtual method if inheriting ◦ Required for polymorphism
- 42. Polymorphism The pets example continued: ◦ void print(Pet &) does not know anything about the two derived classes ◦ Compiler does not consider the derived classes at all, while compiling this function ◦ Still the corresponding sounds gets printed. ◦ Because the exact method to be called is determined during the run-time ◦ virtual keyword is required for this process ◦ Single interface talk() can invoke many different implementations depending on the type ◦ Thus called “polymorphic”
- 43. Pure Virtual Methods ◦ We didn’t need the function returning “???”, and we can just put =0 instead ◦ This method has no definition, and is called a pure virtual method ◦ A class with a pure virtual method is called an abstract class, as opposed to a concrete class ◦ An abstract class cannot be instantiated directly, and derived types must be used ◦ A derived type must override all pure virtual methods, otherwise it becomes abstract too
- 44. Access Specifier: protected Protected members are accessible only from a derived class public protected private this class Yes Yes Yes derived classes Yes Yes No elsewhere Yes No No
- 45. Destructor Class may manage resources ◦ e.g. files, connections to web ◦ malloc’ed memory buffer ◦ Resource handles, like SNDFILE * ◦ that have to be cleaned up / closed Destructor is responsible of ◦ Safely closing any open resources Called when object’s lifetime ends ◦ A local variable gets out of scope ◦ An object is delete’ed ◦ Program exits (global variables)
- 46. RAII Acronym for Resource Acquisition Is Initialization Resource usage is encapsulated in the lifetime of an object ◦ Constructor acquires the resource or throws an exception when it cannot ◦ Destructor releases the resource and never throws exceptions Using the resource is always through an instance of a RAII-class ◦ Guarantees that the resource is available, whenever an instance is reachable ◦ Prevents unwanted access to resources after being released ◦ Makes sure to release the resource properly To make the most out of RAII, ◦ Limit the scope of a variable to where it is actually being used ◦ When it is dynamically allocated, be sure to delete
- 47. std::fstream A good example of RAII ◦ File is closed as fstream exits the scope A good example of polymorphism The same function print() works on both console output and file output Replaces fopen/fprintf/fclose
- 48. Summary of OOP Concepts Abstraction ◦ In many levels, of data (encapsulation), hierarchy (inheritance), behavior (polymorphism) Encapsulation ◦ Information hiding, with private, protected, or public access specifiers ◦ Provide users only what they need to know, to make it easier to use and prevent misuse Inheritance ◦ Subclass can extend base class inheriting its data and behavior ◦ Can build a hierarchy of classes, representing “is a” relationships Polymorphism ◦ Behavior of a method can be different, depending on the subclass
- 50. The Standard Template Library In C, the closest thing that we had to a data structure is array of structs So we had to implement our own as we go ◦ Queue of visited cells for breadth-first search in a maze ◦ Hash map for searching phone book by the last name ◦ Linked list of phone book entries, using chain parameter However, the implementation had to be specific to the element type ◦ There is void *, but it throws away any type information and safety STL allows a generic implementation regardless of types, using templates ◦ e.g. queue<Cell>, map<string, PhoneBookEntry>, list<PhoneBookEntry>
- 51. Containers There are a lot of data structures made for storing collection of data ◦ Sequence containers ◦ vector, array, list, forward_list ◦ Each has different efficiency for random access, insertion, and deletion ◦ Sequence container adapters ◦ stack, queue, priority_queue ◦ Ordered associative containers ◦ set, map, multiset, multimap ◦ Unordered associative (hash) containers ◦ unordered_set, unordered_map, unordered_multiset, unordered_multimap In C, had to go with own implementation always ◦ There is no de-facto standard containers library or something close to that ◦ Partly due to the lack of templates
- 53. std::array<T, N> Contains a fixed-length array ◦ Same performance as C array, as it does not dynamically allocate memory Conforms with other STL containers ◦ Supports size(), front(), back() etc. ◦ Can produce iterators, to be covered later
- 54. std::list<T> Implementation of doubly-linked list Compared to vector/array ◦ Faster insertion in the middle ◦ No spurious delay for insertion due to reallocation ◦ Same O(n) complexity for sequential traverse ◦ Relatively inefficient memory usage overall ◦ O(n) random access, as opposed to vector/array’s O(1)
- 55. std::forward_list<T> Does not have “backwards” link ◦ Can only traverse from the beginning, which is enough for many use cases ◦ Same time complexity for insertion, deletion, traversal, random access ◦ Slightly higher memory efficiency ◦ No size(), back(), push_front() available – have to use iterators
- 56. std::stack<T> First-in, last-out data structure ◦ push(), pop(), top() ◦ Can optionally replace the back-end data structure ◦ Anything that supports push_back(), pop_back(), and back().
- 59. std::set<T> Contains a set of unique items ◦ Efficient for checking existence of items, number of unique items std::set<T>: based on binary search tree ◦ Automatically sorts the items, logarithmic time lookup std::unordered_set<T>: based on hash ◦ Not ordered, constant time lookup
- 60. std::map<K, V> Associative container – retrieve a value associated with given key std::map<K, V>: based on binary search tree ◦ Automatically sorts the items based on key, logarithmic time lookup std::unordered_map<K, V>: based on hash ◦ Not ordered, constant time lookup
- 63. Iterators: find() Searches a container and returns an iterator pointing to the found item ◦ or container.end() if not found std::find() performs the same job ◦ Also usable for containers with non-constant time lookup
- 64. Algorithms std::find() is one of the functions in the algorithms library In C, there were only two: qsort and bsearch Curated list of C++ algorithms ◦ for_each, count, find, search ◦ copy, fill, transform, generate, swap, reverse, rotate, shuffle, unique ◦ is_sorted, sort, partial_sort, stable_sort, nth_element ◦ is_heap, make_heap, push_heap, pop_heap ◦ max, max_element, min, min_element, minmax, minmax_element ◦ is_permutation, next_permutation, prev_permutation ◦ accumulate, inner_product, adjacent_difference, partial_sum, reduce
- 67. std::shared_ptr Dynamically allocated objects are useful when an instance is ‘shared’ ◦ So having it as a local variable is not very feasible But having to remember and control exactly when to delete them is difficult! ◦ Difficult also means dangerous ◦ Continuing the “making it harder to shoot yourself in the foot” philosophy ◦ References to an object is counted, and gets deleted automatically when it reaches 0 ◦ Can be used just like regular pointers Similar: std::unique_ptr ◦ Instead of reference counting, only one pointer can own the access
- 69. The SOLID Principles A mnemonic acronym for 5 basic principles of OOP design Single Reponsibility Principle ◦ A class should have only a single responsibility Open/Closed Principle ◦ Software entities should be open for extension, but closed for modification Liskov Substitution Principle ◦ Objects should be replaceable with a subtype without altering the correctness Interface Segregation Principle ◦ Many client-specific interfaces are better than one general-purpose interface Dependency Inversion Principle ◦ One should depend upon abstractions, not concretions
- 70. Single Responsibility Principle A class should have only one responsibility which ◦ Should be entirely encapsulated by the class ◦ Should be apparent by looking at the name ◦ Robert C Martin: “A class should have only one reason to change” Good example ◦ A report printer program may have two reasons to change, thus has ◦ A class representing the content of a report ◦ A class representing the format of a report Bad example ◦ There is only one big class that basically have all functions of a program ◦ Just like C, but inside a class!
- 73. Interface Segregation Principle Interfaces ◦ Usually means a class with only pure virtual functions C++ Supports multiple inheritance ◦ Segregate interfaces to the simplest unit ◦ Multiple inheritance for a versatile class
- 76. PortAudio C++
- 81. Summary C++ as a whole package ◦ Provides tons of modern facilities for programmers to utlize ◦ Object-Oriented Programming ◦ Functional Programming ◦ Generic Programming ◦ Don’t be scared, just pick any subset you would like ◦ More library options that will help you explore ideas ◦ In some sense, C++ is the final boss of programming languages