moduleceylon.ast.core1.3.3
Source Code
ceylon.ast.core
classIfElseExpression
extends ConditionalExpression
OverviewPackageInitializerAttributesMethods

An if/then/else conditional expression, that is, the keyword ‘if’, followed by a condition list, the keyword ‘then’, followed by an expression, and the keyword ‘else’, followed by another expression.

The then and else expressions are both parsed with a precedence just below the then (ThenOperation) and else (ElseOperation) operations, to avoid ambiguity with these. Alternatively, they may be if/then/else expressions (IfElseExpression) or let expressions (LetExpression).

Examples (multi-line):

if (is Person p)
then p.name
else p.string

if (exists youngest = peopleSortedByAge.first, youngest.age >= 18)
then true
else false

no subtypes hierarchy

Initializer
IfElseExpression(Conditions conditions, DisjoiningExpression|IfElseExpression|LetExpression thenExpression, DisjoiningExpression|IfElseExpression|LetExpression elseExpression)
Parameters:
  • conditions

    The conditions that need to be satisfied to evaluate to the then expression (thenExpression).

  • thenExpression

    The expression that is evaluated if the conditions are satisfied.

  • elseExpression

    The expression that is evaluated if the conditions aren’t satisfied.

Attributes
childrenSource Codeshared actual [Conditions, DisjoiningExpression|IfElseExpression|LetExpression, DisjoiningExpression|IfElseExpression|LetExpression] children

The child nodes of this node.

Refines Expression.children ultimately refines Node.children
conditionsSource Codeshared Conditions conditions

The conditions that need to be satisfied to evaluate to the then expression (thenExpression).

elseExpressionSource Codeshared DisjoiningExpression|IfElseExpression|LetExpression elseExpression

The expression that is evaluated if the conditions aren’t satisfied.

hashSource Codeshared 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.

In general, hash values vary between platforms and between executions of the same program.

Note that when executing on a Java Virtual Machine, the 64-bit Integer value returned by an implementation of hash is truncated to a 32-bit integer value by taking the exclusive disjunction of the 32 lowest-order bits with the 32 highest-order bits, before returning the value to the caller.

Refines Object.hash
thenExpressionSource Codeshared DisjoiningExpression|IfElseExpression|LetExpression thenExpression

The expression that is evaluated if the conditions are satisfied.

Inherited Attributes
Attributes inherited from: Expression
children
Attributes inherited from: Node
children, data, string
Attributes inherited from: Object
hash, string
Methods
copySource Codeshared IfElseExpression copy(Conditions conditions = ..., DisjoiningExpression|IfElseExpression|LetExpression thenExpression = ..., DisjoiningExpression|IfElseExpression|LetExpression elseExpression = ...)
Parameters:
  • conditions = conditions = t
  • thenExpression = nExpression = this.
  • elseExpression = eExpression = this.
equalsSource Codeshared actual Boolean equals(Object that)

Determine if two values are equal.

For any two non-null objects x and y, x.equals(y) may be written as:

x == y

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.

Note that an implementation of equals() that always returns false does satisfy the constraints given above, as long as the class does not inherit Identifiable. Therefore, in very rare cases where there is no reasonable definition of value equality for a class, for example, function references (Callable), it is acceptable for equals() to be defined to return false for every argument.

Refines Object.equals
transformSource Codeshared 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.

Refines Node.transform
visitSource Codeshared 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
copyExtraInfoTo(), delete(), get(), getObject(), put(), remove(), set(), transform(), transformChildren(), visit(), visitChildren()
Methods inherited from: Object
equals