Software Engineers Handbook/Language Dictionary/Multi-paradigmed/C++
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[edit] C++
C++ is an Multi-paradigmed programming language derived from C.
[edit] Type
C++ is a full, Multi-paradigmed programming language implementing the following paradigmen: generic (template metaprogramming), imperative and object-oriented (class-based)
[edit] Execution Entry Point
An executable starts with the main() method.
[edit] General Syntax
The typical statement is completed by a semi-colon. For the assignment of b to a use:
a = b;
[edit] Comments
// this is an inline comment. Everything after the // is a comment.
Block comments are specified by a starting /* and ending */ They can span multiple lines.
/* * this is a block comment */
[edit] Variable Declarations
Declarations can appear anywhere in the implementation.
Declare i as an integer:
int i;
Here are two ways to declare i as an integer and give it an initial value of 0:
int i = 0; int i(0);
[edit] Method Declaration/Implementation
Methods are declared by specifying the interface for the method. It is often declared within the scope of a class.
return_type function_name(argument_1_type arg_1_name,
argument_2_type arg_2_name,
default_argument_type default_arg_name = default_arg_value);
Method implementation repeats much of the same information
return_type class_name::function_name(argument_1_type arg_1_name,
argument_2_type arg_2_name,
default_argument_type default_arg_name)
{
// work with arg_1_name, arg_2_name, and default_arg_name
// depending on the argument types the variables are passed by
// value, reference, or are constant
// don't forget to return something of the return type
return 36;
}
IMPORTANT POINT A beginner in C/C++ might get confused about the distinction between how pointers are declared in a function prototype vs. how the function is defined. For example, if my_function does not return anything, but accepts one floating point input, its function prototype looks as follows:
void my_function(float *some_variable);
However, if the variable my_var is defined to be a pointer to a float, for example:
float *my_var;
Then the manner in which my_function is invoked is as follows:
my_function(my_var);
Beginners sometimes get confused about the fact that a "*" is used to tell the compiler in a prototype statment that a variable is a pointer, but a "*" is not syntactically used during invocation of a function that accepts a pointer as input.
[edit] Scope
Scope is defined by curly braces.
{ // this the the beginning of a scope
// the scope is about to end
}
[edit] Conditional Statements
If and only if A is equal to B assign C to D, otherwise, assign E to F.
if( A == B )
{
D = C;
// more code can be added here. It is used if and only if A is equal to B
}
else
{
F = E;
// more code can be added here. It is used if and only if A is not equal to B
}
or
if( A == B )
D = C; //more lines of code are not permitted after this statement
else
F = E;
Alternatively, a switch statement can be used for multiple choice operations. This sample converts a number input to text.
switch( number_value )
{
case 37:
text = "thirty-seven";
break; // this line prevents the program from writing over this value with the
// following code
case 23:
text = "twenty-three";
break;
default: // this is used if none of the previous cases contain the value
text = "unknown number";
}
[edit] Looping Statements
This code counts from 0 to 9, adding up the contents of the array.
int i = 0;
for( int index = 0; index < 10; index = index + 1 )
{
i = array[index];
}
This code repeats until the number 4 is found. If this runs off of the end of the array, there could be a problem.
int index = 0;
while( 4 != array[index] )
{
index = index + 1;
}
This code increments the counter before the check is made, so that it starts with element 1.
int index = 0;
do
{
index = index + 1;
}
while( 4 != array[index] );
[edit] Output Statements
printf( "%s","Hello world!\n" );
or
std::cout << "Hello world!" << std::endl;
[edit] Containers
The standard template library has a variety of containers including vector, bit-set, list, map and multi-set.
[edit] Algorithms
The standard template library has a variety of algorithms including sort, remove_if, and find_if.
[edit] Garbage collection
Garbage collection is manual.
[edit] Physical Structure
Generally the interfaces are defined in header files, often *.h. The implementation files are often named *.cpp. Useful collections of classes can be compiled into libraries, often *.dll, *.a, or *.so, which can be compiled into executables (statically linked) or used on the fly (dynamically linked).
[edit] Tips
Don't confuse these two:
= // assignment == // comparison, is equal to
Often using the one you don't want will compile, and will produce results you did not expect.
A good practice is to write; if(CONSTANT == variable) rather than if(variable == CONSTANT) since the compiler will catch; if(CONSTANT = variable) but not if(variable = CONSTANT).
Arrays start with index 0.
[edit] Web References
[edit] Books and Articles
- Herbert Schildt's C++: The Complete Reference (ISBN 0072226803) contains dictionary-like listings of code syntax and usage. The structure does not make it useful to learn the language from scratch. However, it could be very useful when switching from a similar language.
- The C++ Standard Library : A Tutorial and Reference by Nicolai M. Josuttis (ISBN 0201379260) contains lengthy and advanced discussions on the standard template library conatiners and algorithms.
- Thinking in C++, Volume 1: Introduction to Standard C++ by Bruce Eckel (ISBN 0139798099) has helped many people make the leap from C to C++. It is available for free online at Bruce Eckel's site.
