moduleceylon.ast.core1.2.2
ceylon.ast.core
classLetExpression
extends Expression
OverviewPackageInitializerAttributesMethods

A let expression, that is, the keyword ‘let’, followed by a list of patterns and an expression that can involve these patterns’ variables.

The expression is parsed with a precedence just below the then (ThenOperation) and else (ElseOperation) operations, to avoid ambiguity with these. Alternatively, it may be an if/then/else expression (IfElseExpression) or a let expression (LetExpression).

Examples:

let ([x,y] = loc, dist = sqrt(x^2 + y^2)) [x / dist, y / dist]
let (c = other.a, d = other.b) Complex(a*c - b*d, a*d + b*c)

no subtypes hierarchy

Initializer
LetExpression(PatternList patterns, DisjoiningExpression|IfElseExpression|LetExpression expression)
Parameters:
  • patterns

    The patterns that the let expression introduces.

  • expression

    The expression.

Attributes
childrenshared actual [PatternList, DisjoiningExpression|IfElseExpression|LetExpression] children

The child nodes of this node.

Refines Expression.children ultimately refines Node.children
expressionshared DisjoiningExpression|IfElseExpression|LetExpression expression

The expression.

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.

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 removal of the 32 highest order bits, before returning the value to the caller.

Refines Object.hash
patternsshared PatternList patterns

The patterns that the let expression introduces.

Inherited Attributes
Attributes inherited from: Expression
children
Attributes inherited from: Node
children, data, string
Attributes inherited from: Object
hash, string
Methods
copyshared LetExpression copy(PatternList patterns = ..., DisjoiningExpression|IfElseExpression|LetExpression expression = ...)
Parameters:
  • patterns = this.patterns
  • expression = this.expression
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.

Note that an implementation of equals() that always returns false does satisfy the constraints given above. 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
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.

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