UnrealScript Language Reference/Language Functionality

UnrealScript Language Reference

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Tim Sweeney
Epic MegaGames, Inc.
tim@epicgames.com
http://www.epicgames.com

Language Functionality

Built-In Operators And Their Precedence

UnrealScript provides a wide variety of C/C++/Java-style operators for such operations as adding numbers together, comaring values, and incrementing variables. The complete set of operators is defined in Object.u, but here is a recap. Here are the standard operators, in order of precedence. Note that all of the C style operators have the same precedence as they do in C.

Operator	Types it applies to	Meaning
`$`	string	String concatenation
`*=`	byte, int, float, vector, rotation	Multiply and assign
`/=`	byte, int, float, vector, rotation	Divide and assign
`+=`	byte, int, float, vector	Add and assign
`-=`	byte, int, float, vector	Subtract and assign
`\|\|`	bool	Logical or
`&&`	bool	Logical and
`&`	int	Bitwise and
`\|`	int	Bitwise or
`^`	int	Bitwise exlusive or
`!=`	all	Compare for inequality
`==`	all	Compare for equality
`<`	byte, int, float, string	Less than
`>`	byte, int, float, string	Greater than
`<=`	byte, int, float, string	Less than or equal to
`>=`	byte, int, float, string	Greater than or equal to
`~=`	float, string	Approximate equality (within 0.0001), case-insensitive equality
`<<`	int, vector	Left shift (int), Forward vector transformation (vector)
`>>`	int, vector	Right shift (int), Reverse vector transformation (vector)
`+`	byte, int, float, vector	Add
`-`	byte, int, float, vector	Subtract
`%`	float	Modulo (remainder after division)
`*`	byte, int, float, vector, rotation	Multiply
`/`	byte, int, float, vector, rotation	Divide
`dot`	vector	Vector dot product
`cross`	vector	Vector cross product
`**`	float	Exponentiation

The above table lists the operators in order of precedence (with operators of the same precedence grouped together). When you type in a complex expression like "1*2+3*4", UnrealScript automatically groups the operators by precedence. Since multiplication has a higher precedence than addition, the expression is evaluated as "(1*2)+(3*4)".

The "&&" (logical and) and "||" (logical or) operators are short-circuited: if the result of the expression can be determined solely from the first expression (for example, if the first argument of && is false), the second expression is not evaluated.

In addition, UnrealScript supports the following unary operators:

Operator	Types it applies to	Meaning
`!`	bool	Logical not
`-`	int, float	negation
`~`	int	bitwise negation
`++, --`	int, float	Increment or Decrement (either before or after a variable)

more on this topic in the Wiki: Operators

General-Purpose Functions

Integer functions:

int Rand( int Max ): Returns a random number from 0 to Max-1.
int Min( int A, int B ): Returns the minimum of the two numbers.
int Max( int A, int B ): Returns the maximum of the two numbers.
int Clamp( int V, int A, int B ): Returns the first number clamped to the interval from A to B.

Floating point functions:

float Abs( float A ): Returns the absolute value of the number.
float Sin( float A ): Returns the sine of the number expressed in radius.
float Cos( float A ): Returns the cosine of the number expressed in radians.
float Tan( float A ): Returns the tangent of the number expressed in radians.
float Atan( float A ): Returns the inverse tangent of the number expressed in radians.
float Exp( float A ): Returns the constant "e" raised to the power of A.
float Loge( float A ): Returns the log (to the base "e") of A.
float Sqrt( float A ): Returns the square root of A.
float Square( float A ): Returns the square of A = A*A.
float FRand(): Returns a random number from 0.0 to 1.0.
float FMin( float A, float B ): Returns the minimum of two numbers.
float FMax( float A, float B ): Returns the maximum of two numbers.
float FClamp( float V, float A, float B ): Returns the first number clamped to the interval from A to B.
float Lerp( float Alpha, float A, float B ): Returns the linear interpolation between A and B.
float Smerp( float Alpha, float A, float B ): Returns an Alpha-smooth nonlinear interpolation between A and B.

Unreal’s string functions have a distinct Basic look and feel:

int Len( coerce string[255] S ): Returns the length of a string.
int InStr( coerce string[255] S, coerce string[255] t): Returns the offset into the first string of the second string if it exists, or -1 if not.
string[255] Mid ( coerce string[255] S, int i, optional int j ): Returns the middle part of the string S, starting and character i and including j characters (or all of them if j is not specified).
string[255] Left ( coerce string[255] S, int i ): Returns the i leftmost characters of s.
string[255] Right ( coerce string[255] S, int i ): Returns the i rightmost characters of s.
string[255] Caps ( coerce string[255] S ): Returns S converted to uppercase.

Vector functions:

float Size( vector A ): Returns the euclidean size of the vector (the square root of the sum of the components squared).
vector Normal( vector A ): Returns a vector of size 1.0, facing in the direction of the specified vector.
Invert ( out vector X, out vector Y, out vector Z ): Inverts a coordinate system specified by three axis vectors.
vector VRand ( ): Returns a uniformly distributed random vector.
float Dist ( vector A, vector B ): Returns the euclidean distance between two points.
vector MirrorVectorByNormal( vector Vect, vector Normal ): Mirrors a vector about a specified normal vector.

more on this topic in the Wiki: Global Function

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