C++ Advanced Features (TCF 2014)

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C++ Advanced Features

Trenton Computer FestivalMarch 15, 2014

Michael P. Redlich@mpredli

about.me/mpredli/

Sunday, March 16, 14

Who’s Mike?

• BS in CS from

• “Petrochemical Research Organization”

• Ai-Logix, Inc. (now AudioCodes)

• Amateur Computer Group of New Jersey

• Publications

• Presentations

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Objectives

• Overloaded Operators

• Templates

• Exception Handling

• Namespaces

• Introduction to the Standard Template Library (STL)

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Overloaded Operators

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What are Overloaded Operators?

• Define basic operations for objects of user-defined types

• as if they were built-in types

• Often referred to as “syntactic sugar”

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// String.h - a simple string class

class String {private:char *string;

public:String(char const *str) {string = new char[strlen(str) + 1];strcpy(string,str);}

~String(void) {delete[] string;}

char *getString(void) const {return string;}

};


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// main application

#include “String.h”

// create two different objects of type StringString string1 = “Hello, C++ Users Group!”;String string2 = “Hello, Java Users Group!”;

// a conditional *without* an overloaded equality operatorif(strcmp(string1.getString(),string2.getString()) == 0)// do this

else// do that

// a conditional *with* an overloaded equality operatorif(string1 == string2)// do this

else// do that


Overloaded Operators (1)

• An overloaded operator has the form:

• T [class::]operatorω(paramList)

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•string1 == string2

• interpreted as string1.operator==(string2);

• string1 is the object in control

• string2 is the argument passed into the operator

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// Equality Operator

bool string::operator==(string const &s) {return(strcmp(getString(),s.getString()) == 0);

}



• Attractive, but can be dangerous!!

• deep vs. shallow copy

• assignment operator side effects

• The compiler automatically generates an assignment operator if one is not explicitly defined

• memberwise assignments

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“Hello, C++ Users Group!”

“Hello, Java Users Group!”

string1.string

string2.string


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// compiler-generated Assignment Operator

string &string::operator=(string const &s) {string = s.string;return *this;}

// main applicationstring1 = string2;



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“Hello, C++ Users Group!”


string1.string

string2.string


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// user-defined Assignment Operator

string &string::operator=(string const &s) {delete[] string;string = new char[strlen(s) + 1];strcpy(string,s);return *this;}

// applicationstring1 = string2;



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string1.string

string2.string



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Operators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be OverloadedOperators Than Can Be Overloaded

+ - * / % ^ & | ~ !

= < > += -+ *= /= %= ^= &=

|= << >> >>= <<= != <= >= &&

|| ++ -- ‘ ->* -> () [] new

delete



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Operators That Cannot Be OverloadedOperators That Cannot Be OverloadedOperators That Cannot Be OverloadedOperators That Cannot Be Overloaded

. .* :: ?:



• Limitations:

• the meaning of an operator cannot be changed

• the number of operands for an operator cannot be changed

• operator precedence and associativity cannot be changed

• no personal operators!!

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Templates

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What are Templates?

• Used for generic programming

• Two kinds:

• class templates

• member function templates

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Templates (1)

• Prototypes:

• template <class T> returnType functionName(paramList) {}

• template <class T> class className {}

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// swap member functions to handle different data types

void swap(int &first,int &second) {int temp = second;second = first;first = temp;}

void swap(float &first,float &second) {float temp = second;second = first;first = temp;}

void swap(char *&first,char *&second) {char *temp = second;second = first;first = temp;}


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/* * function template to swap two elements * of any data type */

template <class T>void swap(T &first,T &second) {T temp = second;second = first;first = temp;}


Templates (2)

• A template specialization is the specific use of a template member function or class

• swap<int>(1,2);

• swap<float>(1.7,3.5);

• swap<char>(‘a’,’b’);

• swap<char *>(“Mets”,”Jets”);

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Exception Handling

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What is Exception Handling?

• A more robust method for handling errors than fastidiously checking for error codes

• error code checking is tedious and can obscure program logic

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Exception Handling (1)

• Throw Expression:

• raises the exception

• Try Block:

• contains a throw expression or a member function that throws an exception

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• Catch Clause(s):

• handles the exception

• defined immediately after the try block

• multiple catch clauses allowed

• no implicit data type conversions

• catch(...) catches any exception type

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C++ Exception Model

• Destructors invoked for all live objects as the stack “unwinds”

• Exception Specification

• specify what type of exception(s) a member function will throw

• Termination vs. Resumption semantics

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// exception handling example

#include <string>#include <stdexcept>

void fred(void) {FILE *file = fopen(“filename.txt”,”rt”);try {if(file == NULL) { // file could not be openedthrow 1;}

int g = george(-1);}

catch(int e) {cout << “ERROR: Could not open file...” << endl;}

catch(string const message) {cout << message << endl;}

// other statements...

}

// continued on next slide...


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// continued from previous slide...

int george(int n) {if(n < 0) {string message = “ERROR: Value less than zero...”;throw message;}


return n;}


C++ Exception Class Hierarchy (1)

• exception

• logic_error (client program errors)

• runtime_error (external errors)

• bad_alloc (memory allocation errors)

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C++ Exception Class Hierarchy (2)

• exception

• bad_cast (dynamic casting errors)

• bad_exception (unexpected())

• bad_typeid (RTTI errors)

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// exception handling example (revised)

#include <string>#include <stdexcept>

void fred(void) {FILE *file = fopen(“filename.txt”,”rt”);try {if(file == NULL) { // file could not be openedthrow runtime_error(“ERROR: Could not open file...”);}

int g = george(-1);}

catch(runtime_error &re) {cout << re.what() << endl;}

catch(string const message) {cout << message << endl;}


}



• Do not throw exceptions:

• to indicate special return values

• in copy constructors and assignment operators

• stroustrup.com/3rd_safe.pdf

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Namespaces

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What are Namespaces?

• Used to prevent global naming conflicts

• All C++ standard library components are contained within a single namespace called std

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// an example of using header files from different sources

// baseball.h...int strike = 0;...

// bowling.h...bool strike = false;...

// main application#include baseball.h#include bowling.h // ERROR: strike already declared


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// an example of using header files from different sources

// baseball.hnamespace baseball {...int strike = 0;...}

// bowling.hnamespace bowling {...bool strike = false;...}

// main application#include baseball.h#include bowling.h // OK!


Namespaces (1)

• Fully-qualified member names:

• namespace name

• scope resolution operator (::)

• member name

• baseball::strike

• bowling::strike

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Aliases

• Provides shorthand for the fully-qualified namespace name

• Has the form:

• namespace m = N;

• namespace bb = baseball;

• namespace bw = bowling;

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Using Directive

• Provides access to all members of a namespace without having to write the fully-qualified namespace member names

• Has the form:

• using namespace N;

• using namespace baseball;

• using namespace bowling;

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Using Declaration

• Provides access to individual members of a namespace without having to write the fully-qualified namespace member names

• Has the form:

• using N::m;

• using baseball::strike;

• using bowling::strike;

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Standard Template Library (STL)

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What is the STL?

• A subset of Standard C++

• First developed by HP Labs in 1994

• Three main parts:

• containers

• iterators

• algorithms

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What are Containers?

• A data structure that contains a sequence of elements

• Sequential containers:

• organize elements linearly

• Sorted associative containers:

• organize elements based on a key

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Containers (1)

• Primarily chosen by how well it can perform certain operations, such as:

• add elements to the container

• remove elements from the container

• rearrange elements within the container

• inspect elements within the container

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Containers (2)

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vector deque list set/map

insert O(n) O(n) O(1) O(nlogn)

prepend O(n) O(1) O(1) O(nlogn)

find O(n) O(n) O(n) O(nlogn)

X[i] O(1) O(1) O(n) O(n)

pointers 0 1 2 3


What are Iterators?

• A generalization of a C/C++ pointer

• Used to access elements within an ordered sequence

• Considered the “glue” that tie together containers and algorithms

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Iterators

• Five types:

• input

• output

• forward

• bi-directional

• random access

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#include <vector>

typedef vector<int>::iterator iteratorvector<int> v(10);for(int i = 0;i < 9;++i) {v.push_back(i);}

iterator current = v.begin();iterator last = v.end();while(current != last) {cout << *current << “\n”;++current;}

0 1 2 3 4 5 6 7 8

current last


What are Algorithms?

• Perform various operations on containers such as:

• searching

• sorting

• transforming

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Algorithms• Non-Mutating

• binary_search

• count

• equal

• find

• Mutating

• copy

• generate

• remove

• reverse

• sort

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Popular C++ Compilers

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• Embarcadero C++ Builder XE5

• embarcadero.com/products/cbuilder

• Microsoft Visual C++

• microsoft.com

• Open Watcom 1.9

• openwatcom.org


Local C++ User Groups

• ACGNJ C++ Users Group

• facilitated by Bruce Arnold

• acgnj.barnold.us

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Further Reading (1)

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• C & C++ Code Capsules

• Chuck Allison

• freshsources.com

• The C++ Programming Language

• Bjarne Stroustrup

• stroustrup.com/4th.html


Further Reading (2)

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• The Annotated C++ Reference Manual

• Margaret Ellis and Bjarne Stroustrup

• stroustrup.com/arm.html

• 1997 C++ Public Review Document

• C++ ISO JTC1/SC22/WG21 Committee

• open-std.org/jtc1/sc22/open/n2356


Upcoming Events (1)

• Trenton Computer Festival

• March 14-15, 2014

• tcf-nj.org

• Emerging Technologies for the Enterprise

• April 22-23, 2014

• phillyemergingtech.com

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Upcoming Events (2)


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Thanks!

[email protected]

@mpredli

javasig.org


mailto:[email protected]

mailto:[email protected]

Technology

C++ Advanced Features (TCF 2014)