Each condition is a boolean expression and must be surrounded by square brackets. A path element is matched with an AST node if all the corresponding conditions are met.

Expressions can be of one of the following types:

BOOL
INT
DOUBLE
TREE (AST nodes)
SEMA (semantic information associated with AST nodes)
STRING

BOOL, INT and DOUBLE values can be converted into each other; TREE and SEMA values can be converted to the BOOL type.

The following types of expressions are supported:

Path expression: Starts with a child qualifier:

[Expr::ExprBinary/Expr1::ExprConst]

Note: When a path expression constitutes the whole KAST pattern, it starts with '//' followed by a node type name. This means that corresponding subtrees are matched anywhere in the AST. On the other hand, when a path expression is one of the conditions or a part of a condition in a KAST expression, it starts with a child name or any other axis qualifier instead. This means that the path must start from the node this expression is related to.

Or expression:

Expression1 | Expression2

Not expression:

not Expression

Function expression:

Func(Expr1, Expr2, ...)

You can use both built-in functions and custom functions.

See Java custom functions.

Dot expression:

Expression.Func(...)

The right part of such expression must be a function call. The expression in the left part of the dot expression is treated as the first argument of the function in the right part: a.b(c) is equivalent to b(a, c).

Attribute expression:

@attribute_name

Arithmetic expression:

Expression1 [+, -, /, *] Expression2

Relational expression:

Expression1 [>, <, >=, <=, =, !=] Expression2

Bracket expression:

(Expression)

Constant expression:

'abc' , 2.0

There are a number of literal representations for integer constants representing operation types, class specifiers, etc.

Variable expression:

$variable

See Variables.

Supported operations

The operations below are ordered by priority, with the highest priority at the top.

(), . not +, - >, >=, <, <= =, != |