Node

rascal-0.40.17

Synopsis

Node values.

Syntax

Exp₀ ( Exp₁, Exp₂, ..., FieldName₁ = Expr₁, FieldName₂ = Expr₂, ... )

Types

Exp₀	Exp₁	Exp₂	...	Exp₀ ( Exp₁, Exp₂, ... )
str	value	value	...	node

Description

Values of type node represent untyped trees and are constructed as follows:

• the string value of Exp₀ is the node name;
• zero or more expressions of type value are the node\'s children.
• optionally, unordered named fields can be added as well.

The following are provided for nodes:

• Equal
• FieldAssignment
• FieldSelection
• GreaterThan
• GreaterThanOrEqual
• LessThan
• LessThanOrEqual
• NotEqual
• Slice
• Subscription

Examples

A node with name "my_node" and three arguments:

rascal>"my_node"(1, true, "abc");
node: "my_node"(1,true,"abc")

A nested node structure:

rascal>"my_node1"(1, "my_node2"(3.5, ["a", "b", "c"]), true);
node: "my_node1"(
  1,
  "my_node2"(
    3.5,
    ["a","b","c"]),
  true)

A node with named fields:

rascal>"my_node2"(1,2,size=2,age=24);
node: "my_node2"(1,2,
  size=2,
  age=24)

Benefits

• nodes are untyped and can be used to quickly import untyped data into Rascal
• pattern matching on nodes is quite expressive

Pitfalls

• the lack of types at run-time makes pattern matching on node possibly inaccurate (you might match more than you think)