Expression Syntax

The WorldEdit expression parser is supposed to work like Java and related languages, with a few subtle differences:

  • Final semicolons can be omitted in most cases.
  • The last value in a sequence is always returned, even without a return statement.
  • The binary infix ^ operator is a power operator instead of an xor operator and has an according priority as well.
  • There is a postfix factorial operator (!).
  • There is a binary infix near operator (~=).
  • No objects :)

Operators

The expression parser uses Java’s precedence rules, with the following exceptions and additions:

  • The binary power operator (^) is between priority 2 and 3
  • The postfix factorial operator (!) has a priority of 2
  • The near operator (~=) has a priority of 7

Binary infix

These operators are put between their two operands.

Arithmetic

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulo
^ Power

Bitwise

These operators interpret their operands as 32 bit integers and operate on their bits.

<< Left-shift
>> Right-shift

Logical

These operators interpret everything greater than zero as true and everything else as false. They return 1 for true and 0 for false.

&& Logical and
|| Logical or

Comparison

These operators compare their operands and return 1 for true and 0 for false.

< less than
> greater than
<= less or equal
>= greater or equal
== equal
!= not equal
~= near

Assignment

These operators require a variable on the left side. Using the simple assignment operator (=) to assign to a non-existant variable creates a temporary variable.

= simple assignment
+= addition+assignment
-= subtraction+assignment
*= multiplication+assignment
/= division+assignment
%= modulo+assignment
^= power+assignment

Prefix

These operators precede the expression they apply to.

Prefix Operators

-x (negation)
~x Bitwise complement (see bitwise binary operators)
!x Logical complement (see logical binary operators)
++x Pre-increment
--x Pre-decrement

Postfix

These operators succeed the expression they apply to.

Postfix Operators

x! Factorial
x++ Post-increment
x-- Post-decrement

Ternary infix

The ternary operator is used to represent a conditional expression in a compact way:

<condition> ? <true-branch> : <false-branch>

It works exactly like the if/else statement, except that the branches can only be single expressions.

Functions

Math Functions

The expression parser provides the following functions from the Java Math library:

abs Returns the absolute value of a number.
acos Returns the arc cosine of a value; the returned angle is in the range 0.0 through pi.
asin Returns the arc sine of a value; the returned angle is in the range -pi/2 through pi/2.
atan2 Returns the angle theta from the conversion of rectangular coordinates (x, y) to polar coordinates (r, theta).
atan Returns the arc tangent of a value; the returned angle is in the range -pi/2 through pi/2.
cbrt Returns the cube root of a value.
ceil Returns the smallest (closest to negative infinity) value that is greater than or equal to the argument and is equal to a mathematical integer.
cos Returns the trigonometric cosine of an angle.
cosh Returns the hyperbolic cosine of a value.
exp Returns Euler’s number e raised to the power of a value.
floor Returns the largest (closest to positive infinity) value that is less than or equal to the argument and is equal to a mathematical integer.
ln Returns the natural logarithm (base e) of a value.
log Returns the natural logarithm (base e) of a value.
log10 Returns the base 10 logarithm (base e) of a value.
max Returns the greatest of the values. (supports 2 and 3 arguments)
min Returns the smallest of the values. (supports 2 and 3 arguments)
rint Returns the number that is closest in value to the argument and is equal to a mathematical integer.
round Returns the closest number to the argument
sin Returns the trigonometric sine of an angle.
sinh Returns the hyperbolic sine of a value.
sqrt Returns the correctly rounded positive square root of a value.
tan Returns the trigonometric tangent of an angle.
tanh Returns the hyperbolic tangent of a value.

Additional Functions

Additionally, it provides the following functions:

rotate(x, y, angle) Rotates the given coordinate pair by the given angle.
swap(x, y) Swaps the contents of the 2 given variables.
random() Returns a random positive number less than 1.0.
randint(max) Returns a random positive integer less than max.

Block Query Functions

The following functions can be used to query blocks in a world in an editting context.

query(x, y, z, type, data) Returns true, if the block at the given coordinates has the given type and data value. If possible, the type and data of the block will be assigned to type and data.
queryRel(dx, dy, dz, type, data) Like query, except with relative world coordinates
queryAbs(xp, yp, zp, type, data) Like query, except with absolute world coordinates

Constants

Constants

The following constants are always available, and cannot be assigned.

e 2.7182818284590452354 The base of the natural logarithm
pi 3.14159265358979323846 The ratio between circumference and diameter of a circle
true 1 for boolean operations
false 0 for boolean operations

Block Statements

Block statements are groups of statements enclosed in braces:

{ x=5; y=6; }

They are mostly used in conjunction with control structures.

Control Structures

if/else

if (<condition>) <true-branch>
if (<condition>) <true-branch> else <false-branch>
  • <condition> is evaluated to decide which branch to execute.
  • Everything greater than zero is interpreted as true and everything else as false.
  • <true-code> and <false-code> can either be single statements delimited with a semicolon or block statements.

Note: An else keyword is always associated with the last if. This allows elseif constructs like these:

if (<condition 1>) <true-code 1> else if (<condition 2>) <true-code 2> else <false-code>

Loops

Loops can at most loop 256 times.

while

while (<condition>) <body>
do <body> while (<condition>);
  • <condition> is evaluated to decide whether to continue looping.
  • <body> can either be a single statement delimited with a semicolon or a block statement.
  • do-while checks the condition after executing the body.

Java/C-style for

for (<init>; <condition>; <increment>) <body>
  • <init>, <condition> and <increment> are single expressions.
  • <body> can either be a single statement delimited with a semicolon or a block statement.

Execution steps

First, <init> is evaluated once, then, each iteration follows these steps:

  1. If <condition> evaluates as less than or equal to zero (i.e. false), the loop is aborted.
  2. <body> is executed.
  3. <increment> is executed.

Simple for

for (<counter> = <first>, <last>) <body>
  • <counter> is a variable used to count the iterations.
  • <first> and <last> are single expressions.
  • <body> can either be a single statement delimited with a semicolon or a block statement.

Execution steps

First, an internal counter is set to <first>. Then, each iteration follows these steps:

  1. If the internal counter exceeds <last>, the loop is aborted.
  2. <counter> is set to the internal counter.
  3. <body> is executed.
  4. <counter> is incremented by 1.0.

<first> and <last> are only evaluated once.