AngelScript
Expressions

Assignments

  lvalue = rvalue;

lvalue must be an expression that evaluates to a memory location where the expression value can be stored, e.g. a variable. An assignment evaluates to the same value and type of the data stored. The right hand expression is always computed before the left.

Compound assignments

  lvalue += rvalue;
  lvalue = lvalue + rvalue;

A compound assignment is a combination of an operator followed by the assignment. The two expressions above means practically the same thing. Except that first one is more efficient in that the lvalue is only evaluated once, which can make a difference if the lvalue is complex expression in itself.

Available operators: += -= *= /= %= **= &= |= ^= <<= >>= >>>=

Function call

  func();
  func(arg);
  func(arg1, arg2);
  lvalue = func();

Functions are called to perform an action, and possibly return a value that can be used in further operations. If a function takes more than one argument, the argument expressions are evaluated in the reverse order, i.e. the last argument is evaluated first.

Some functions are declared with output reference parameters to return multiple values. When calling such functions the output parameter must be given as an expression that can be assigned with the returned value. If the additional output value won't be used use the special argument 'void' to tell the compiler that.

  // This function returns a value in the output parameter
  void func(int &out outputValue)
  {
    outputValue = 42;
  }
  // Call the function with a valid lvalue expression to receive the output value
  int value;
  func(value);
  // Call the function with 'void' argument to ignore the output value
  func(void);

Arguments can also be named and passed to a specific argument independent of the order the parameters were declared in. No positional arguments may follow any named arguments.

  void func(int flagA = false, int flagB = false, int flagC = false) {}
  // Call the function, setting only a subset of its parameters
  func(flagC: true);
  func(flagB: true, flagA: true);

Type conversions

  // implicitly convert the clss handle to a intf handle
  intf @a = @clss();
  // explicitly convert the intf handle to a clss handle
  clss @b = cast<clss>(a);

Object handles can be converted to other object handles with the cast operator. If the cast is valid, i.e. the true object implements the class or interface being requested, the operator returns a valid handle. If the cast is not valid, the cast returns a null handle.

The above is called a reference cast, and only works for types that support object handles. In this case the handle still refers to the same object, it is just exposed through a different interface.

Types that do not support object handles can be converted with a value cast instead. In this case a new value is constructed, or in case of objects a new instance of the object is created.

  // implicit value cast
  int a = 1.0f;
  // explicit value cast
  float b = float(a)/2;

In most cases an explicit cast is not necessary for primitive types, however, as the compiler is usually able to do an implicit cast to the correct type.

Math operators

  c = -(a + b);
operatordescriptionleft handright handresult
+ unary positive   NUM NUM
- unary negative   NUM NUM
+ addition NUM NUM NUM
- subtraction NUM NUM NUM
* multiplication NUM NUM NUM
/ division NUM NUM NUM
% modulos NUM NUM NUM ** exponent NUM NUM NUM

Plus and minus can be used as unary operators as well. NUM can be exchanged for any numeric type, e.g. int or float. Both terms of the dual operations will be implicitly converted to have the same type. The result is always the same type as the original terms. One exception is unary negative which is not available for uint.

Bitwise operators

  c = ~(a | b);
operator description left handright handresult
~ bitwise complement   NUM NUM
& bitwise and NUM NUM NUM
| bitwise or NUM NUM NUM
^ bitwise xor NUM NUM NUM
<< left shift NUM NUM NUM
>> right shift NUM NUM NUM
>>>arithmetic right shiftNUM NUM NUM

All except ~ are dual operators.

Both operands will be converted to integers while keeping the sign of the original type before the operation. The resulting type will be the same as the left hand operand.

Logic operators

  if( a and b or not c )
  {
    // ... do something
  }
operator description left hand right handresult
notlogical not   boolbool
andlogical and boolboolbool
or logical or boolboolbool
xorlogical exclusive orboolboolbool

Boolean operators only evaluate necessary terms. For example in expression a and b, b is only evaluated if a is true.

Each of the logic operators can be written as symbols as well, i.e. || for or, && for and, ^^ for xor, and ! for not.

Equality comparison operators

  if( a == b )
  {
    // ... do something
  }

The operators == and != are used to compare two values to determine if they are equal or not equal, respectively. The result of this operation is always a boolean value.

Relational comparison operators

  if( a > b )
  {
    // ... do something
  }

The operators <, >, <=, and >= are used to compare two values to determine their relationship. The result is always a boolean value.

Identity comparison operators

  if( a is null )
  {
    // ... do something
  }
  else if( a is b )
  {
    // ... do something
  }

The operators is and !is are used to compare the identity of two objects, i.e. to determine if the two are the same object or not. These operators are only valid for reference types as they compare the address of two objects. The result is always a boolean value.

Increment operators

  // The following means a = i; i = i + 1;
  a = i++;
  // The following means i = i - 1; b = i;
  b = --i;

These operators can be placed either before or after an lvalue to increment/decrement its value either before or after the value is used in the expression. The value is always incremented or decremented with 1.

Indexing operator

  arr[i] = 1;

This operator is used to access an element contained within the object. Depending on the object type, the expression between the [] needs to be of different types.

Conditional expression

  choose ? a : b;

If the value of choose is true then the expression returns a otherwise it will return b. Both a and b must be of the same type.

If they are not of the same type the compiler will attempt an implicit conversion using the following rules. If the a expression is 0 or null, then the compiler will attempt to convert it to the type of b, otherwise it will attempt to convert b to the type of a.

If the conversion doesn't work, then the compiler will give an error.

Member access

  object.property = 1;
  object.method();

object must be an expression resulting in a data type that have members. property is the name of a member variable that can be read/set directly. method is the name of a member method that can be called on the object.

Handle-of

  // Make handle reference the object instance
  @handle = @object;
  // Clear the handle and release the object it references
  @handle = null;

Object handles are references to an object. More than one handle can reference the same object, and only when no more handles reference an object is the object destroyed.

The members of the object that the handle references are accessed the same way through the handle as if accessed directly through the object variable, i.e. with . operator.

See Also
Object handles

Parenthesis

  a = c * (a + b);
  if( (a or b) and c )
  {
    // ... do something
  }

Parenthesis are used to group expressions when the operator precedence does not give the desired order of evaluation.

Scope resolution

  int value;
  void function()
  {
    int value;       // local variable overloads the global variable
    ::value = value; // use scope resolution operator to refer to the global variable 
  } 

The scope resolution operator :: can be used to access variables or functions from another scope when the name is overloaded by a local variable or function. Write the scope name on the left (or blank for the global scope) and the name of the variable/function on the right.

See Also
Namespaces

Anonymous objects

Anonymous objects, i.e. objects that are created without being declared as variables, can be instantiated in expressions by calling invoking the object's constructor as if it was a function. Both reference types and value types can be created like this.

  // Call the function with a new object of the type MyClass
  func(MyClass(1,2,3));

For types that support it, the anonymous objects can also be initialized with initialization lists.

  // Call the function with a dictionary
  func(dictionary = {{'banana',1}, {'apple',2}, {'orange',3}});