allmd/01_basics.md

C++\

Fundamentals

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Intrinsic Data Types

Basic Type	Variant(s)
bool
char	unsigned
int	unsigned, long, short
float
double	long
void

Note, void is the "anti-datatype", used in functions returning nothing

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Operators

Purpose	Symbols
Math	+ - * / % += -= /= %= ++ --
Comparison	< > <= >= != ==
Logical Comparison	`&&
Memory	* & new delete sizeof
Assignment	=
Member Access	-> .
Name Resolution	::

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Curly Braces { }

Used to group statements together and to define the scope of a function

Creates new layer of scope

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Expressions

Composite mathematical expressions:

a = b * (c - 4) / d++;

Composite boolean expressions:

if (a && b && f()) { e = a; }

Note, Operators && and || use "short-circuiting," so "b" and "f()" in the example above may not get evaluated.

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Scope resolution operator:

t = std::pow(r, 2);
b = std::sqrt(d);

Dot and Pointer Operator:

t = my_obj.someFunction();
b = my_ptr->someFunction();

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Type Casting

float pi = 3.14;

int approx_pi = static_cast<int>(pi);

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Limits to Type Casting

Does not work to change to fundamentally different types

float f = (float) "3.14";   // won't compile

Be careful with your assumptions

unsigned int huge_value = 4294967295; // ok
int i = static_cast<int>(huge_value); // won't work!

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Control Statements

For, While, and Do-While Loops:

for (int i=0; i<10; ++i) { }
while (boolean-expression)  { }
do { } while (boolean-expression);

If-Then-Else Tests:

if (boolean-expression) { }
else if (boolean-expression) { }
else { }

In the previous examples, +boolean-expression+ is any valid C++ statement which results in true or false, such as:

• if (0) // Always false
• while (a > 5)

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Declarations and Definitions

In C++ we split our code into multiple files

• headers (*.h)
• bodies (*.C)

Headers generally contain +declarations+

• Statement of the types we will use
• Gives names to types

Bodies generally contain +definitions+

• Our descriptions of those types, including what they do or how they are built
• Memory consumed
• The operations functions perform

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Declaration Examples

Free functions:

returnType functionName(type1 name1, type2 name2);

Object member functions (methods):

class ClassName
{
  returnType methodName(type1 name1, type2 name2);
};

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Definition Examples

Function definition:

returnType functionName(type1 name1, type2 name2)
{
  // statements
}

Class method definition:

returnType ClassName::methodName(type1 name1, type2 name2)
{
   // statements
}

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Make

A Makefile is a list of dependencies with rules to satisfy those dependencies All MOOSE-based applications are supplied with a complete Makefile To build a MOOSE-based application just type:

make