int var = 0, var2 = 10; object@ handle, handle2; const float pi = 3.141592f;
Variables must be declared before they are used within the statement block, or any sub blocks. When the code exits the statement block where the variable was declared the variable is no longer valid.
A variable can be declared with or without an initial expression. If it is declared with an initial expression it, the expression must have the evaluate to a type compatible with the variable type.
Any number of variables can be declared on the same line separated with commas, where all variables then get the same type.
Variables can be declared as const. In these cases the value of the variable cannot be changed after initialization.
Variables of primitive types that are declared without an initial value, will have a random value. Variables of complex types, such as handles and object are initialized with a default value. For handles this is null, for objects this is what is defined by the object's default constructor.
a = b; // a variable assignment func(); // a function call
Any expression may be placed alone on a line as a statement. This will normally be used for variable assignments or function calls that don't return any value of importance.
All expression statements must end with a ;.
if( condition )
{
// Do something if condition is true
}
if( value < 10 )
{
// Do something if value is less than 10
}
else
{
// Do something else if value is greater than or equal to 10
}
If statements are used to decide whether to execute a part of the logic or not depending on a certain condition. The conditional expression must always evaluate to true or false.
It's possible to chain several if-else statements, in which case each condition will be evaluated sequencially until one is found to be true.
switch( value )
{
case 0:
// Do something if value equals 0, then leave
break;
case 2:
case constant_value:
// This will be executed if value equals 2 or the constant_value
break;
default:
// This will be executed if value doesn't equal any of the cases
}
If you have an integer (signed or unsigned) expression that have many different outcomes that should lead to different code, a switch case is often the best choice for implementing the condition. It is much faster than a series of ifs, especially if all of the case values are close in numbers.
Each case should be terminated with a break statement unless you want the code to continue with the next case.
The case value can be a constant variable that was initialized with a constant expression. If the constant variable was initialized with an expression that cannot be determined at compile time it cannot be used in the case values.
// Loop, where the condition is checked before the logic is executed
int i = 0;
while( i < 10 )
{
// Do something
i++;
}
// Loop, where the logic is executed before the condition is checked
int j = 0;
do
{
// Do something
j++;
} while( j < 10 );
For both while and do-while the expression that determines if the loop should continue must evaluate to either true or false. If it evaluates to true, the loop continues, otherwise it stops and the code will continue with the next statement immediately following the loop.
// More compact loop, where condituion is checked before the logic is executed
for( int n = 0; n < 10; n++ )
{
// Do something
}
The for loop is a more compact form of a while loop. The first part of the statement (until the first ;) is executed only once, before the loop starts. Here it is possible to declare a variable that will be visible only within the loop statement. The second part is the condition that must be satisfied for the loop to be executed. A blank expression here will always evaluate to true. The last part is executed after the logic within the loop, e.g. used to increment an iteration variable.
for(;;) // endless loop
{
// Do something
// End the loop when condition is true
if( condition )
break;
}
break terminates the smallest enclosing loop statement or switch statement.
for(int n = 0; n < 10; n++ )
{
if( n == 5 )
continue;
// Do something for all values from 0 to 9, except for the value 5 }
continue jumps to the next iteration of the smallest enclosing loop statement.
float valueOfPI()
{
return 3.141592f; // return a value
}
Any function with a return type other than void must be finished with a return statement where expression evaluates to the same data type as the function return type. Functions declared as void can have return statements without any expression to terminate early.
{
int a;
float b;
{
float a; // Override the declaration of the outer variable
// but only within the scope of this block.
// variables from outer blocks are still visible
b = a;
}
// a now refers to the integer variable again }
A statement block is a collection of statements. Each statement block has its own scope of visibility, so variables declared within a statement block are not visible outside the block.
1.5.9