An existence condition, that is, the keyword ‘exists’, followed by either a specified pattern or a member name referencing an existing value.

Examples:

exists name
exists firstItem = first?.item

no subtypes hierarchy

Initializer
ExistsCondition(SpecifiedPattern|MemberName tested, Boolean negated = false)
Parameters:
  • tested

    The value reference or pattern specification being tested.

  • negated = false

    Whether the condition is negated or not.

    If the condition is negated, the ‘exists’ keyword is prefixed by a negation operator ‘!’.

Attributes
childrenshared actual [SpecifiedPattern|LIdentifier] children

The child nodes of this node.

hashshared actual Integer hash

The hash value of the value, which allows the value to be an element of a hash-based set or key of a hash-based map. Implementations must respect the constraint that:

  • if x==y then x.hash==y.hash.

Therefore, a class which refines equals must also refine hash.

Because the Integer type is platform-dependent a compiler for a given platform is permitted to further manipulate the calculated hash for an object, and the resulting hash may differ between platforms.

Refines Object.hash
negatedshared actual Boolean negated

Whether the condition is negated or not.

If the condition is negated, the ‘exists’ keyword is prefixed by a negation operator ‘!’.

testedshared actual SpecifiedPattern|MemberName tested

The value reference or pattern specification being tested.

Inherited Attributes
Attributes inherited from: ExistsOrNonemptyCondition
Attributes inherited from: Node
Attributes inherited from: Object
hash, string
Methods
copyshared ExistsCondition copy(SpecifiedPattern|MemberName tested = ..., Boolean negated = ...)
Parameters:
  • tested = this.tested
  • negated = this.negated
equalsshared actual Boolean equals(Object that)

Determine if two values are equal. Implementations should respect the constraints that:

  • if x===y then x==y (reflexivity),
  • if x==y then y==x (symmetry),
  • if x==y and y==z then x==z (transitivity).

Furthermore it is recommended that implementations ensure that if x==y then x and y have the same concrete class.

A class which explicitly refines equals() is said to support value equality, and the equality operator == is considered much more meaningful for such classes than for a class which simply inherits the default implementation of identity equality from Identifiable.

Refines Object.equals
transformshared actual Result transform<out Result>(Transformer<Result> transformer)

Transform this node with the given transformer by calling the appropriate transformX method on the transformer.

If you have a Node node that’s actually an LIdentifier instance, then the runtime will call LIdentifier.transform; therefore, this method is by nature narrowing. This means that if transformer is a NarrowingTransformer, calling node.transform(transformer) is equivalent to calling transformer.transformNode(node). On the other hand, if transformer is a WideningTransformer, then the two operations are very different.

visitshared actual void visit(Visitor visitor)

Visit this node with the given visitor. Calls the appropriate visitX method on the visitor.

Refines Node.visit
Inherited Methods
Methods inherited from: Node
Methods inherited from: Object
equals