A Toy Language Interpreter

Transcript

1. A Toy Language Interpreter Ionuț G. Stan · BJUG #28 · December 2014
2. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Plan ‣ Interpreters and Compilers ‣ Why Learn Compilers ‣ Why Scala for Today ‣ Coding Part
3. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters and Compilers
4. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters Interpreter Result Source
5. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters Parser Interpreter Result Source
6. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters Parser Interpreter Result Source AST (Abstract Syntax Tree)
7. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters Lexer Parser Interpreter Result Source
8. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Interpreters Lexer Parser Type Checker Interpreter Source Result
9. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Compilers Compiler Target Source
10. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Compilers Compiler Target Interpreter Result Source
11. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Compilers Lexer Parser Type Checker Code Emitter Source Target
12. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Many Other Phases Lexer Parser Type Checker Source Target ...
13. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Today Parser Interpreter Result Source AST (Abstract Syntax Tree)
14. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers
15. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
16. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
17. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
18. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
19. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
20. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
21. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
22. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Learn Compilers ‣ This is my motivation ‣ I like looking under the hood ‣ A compiler's hood is like a starship's hood ‣ Compilers are really well documented ‣ You get to understand tricky language concepts ‣ You get to understand modular architecture ‣ Useful for (E)DSLs development ‣ It's fun!
23. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala
24. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ But... there's one missing feature in Java 8 ‣ The closest alternative is the Visitor pattern ‣ But that's a cumbersome pattern ‣ Last, but not least, I write Scala daily :-)
25. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though ‣ The closest alternative is the Visitor pattern ‣ But that's a cumbersome pattern ‣ Last, but not least, I write Scala daily :-)
26. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though: pattern matching ‣ The closest alternative is the Visitor pattern ‣ But that's a cumbersome pattern ‣ Last, but not least, I write Scala daily :-)
27. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Scala trait Node! case class Num(value: Int) extends Node! case class Add(left: Node, right: Node) extends Node! ! val ast = Add(Num(1), Num(2))! ! val sum = ast match {! case Add(Num(a), Num(b)) => a + b! }
28. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Scala trait Node! case class Num(value: Int) extends Node! case class Add(left: Node, right: Node) extends Node! ! val ast = Add(Num(1), Num(2))! ! val sum = ast match {! case Add(Num(a), Num(b)) => a + b! }
29. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Scala trait Node! case class Num(value: Int) extends Node! case class Add(left: Node, right: Node) extends Node! ! val ast = Add(Num(1), Num(2))! ! val sum = ast match {! case Add(Num(a), Num(b)) => a + b! }
30. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Scala trait Node! case class Num(value: Int) extends Node! case class Add(left: Node, right: Node) extends Node! ! val ast = Add(Num(1), Num(2))! ! val sum = ast match {! case Add(Num(a), Num(b)) => a + b! }
31. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Scala trait Node! case class Num(value: Int) extends Node! case class Add(left: Node, right: Node) extends Node! ! val ast = Add(Num(1), Num(2))! ! val sum = ast match {! case Add(Num(a), Num(b)) => a + b! }
32. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though: pattern matching ‣ The closest alternative is the Visitor pattern ‣ But that's a cumbersome pattern ‣ Last, but not least, I write Scala daily :-)
33. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Java public interface Node {}! ! public class Num implements Node {! public final int value;! public Num(int value) { this.value = value; }! }! ! public class Add implements Node {! public final Node left, right;! public Add(Node left, Node right) {! this.left = left;! this.right = right;! }! }
34. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Java public interface Node {}! ! public class Num implements Node {! public final int value;! public Num(int value) { this.value = value; }! }! ! public class Add implements Node {! public final Node left, right;! public Add(Node left, Node right) {! this.left = left;! this.right = right;! }! }
35. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Representing an AST in Java public interface Node {}! ! public class Num implements Node {! public final int value;! public Num(int value) { this.value = value; }! }! ! public class Add implements Node {! public final Node left, right;! public Add(Node left, Node right) {! this.left = left;! this.right = right;! }! }
36. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java public interface Node {! public <R> R match(Matcher<R> matcher);! }! ! public interface Matcher<R> {! public R matchNum(Num n);! public R matchAdd(Add a);! }
37. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java public class Num implements Node {! // fields and constructor omitted! ! @Override! public <R> R match(Matcher<R> matcher) {! return matcher.matchNum(this);! }! }
38. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java public class Add implements Node {! // fields and constructor omitted! ! @Override! public <R> R match(Matcher<R> matcher) {! return matcher.matchAdd(this);! }! }
39. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java int ast = new Add(new Num(1), new Num(2));! ! int sum = ast.match(new Matcher<Integer> {! @Override! public R matchNum(Num n) {! return n.value;! }! ! @Override! public R matchAdd(Add a) {! int left = a.left.match(this);! int right = a.right.match(this);! return left + right;! }! });
40. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java int ast = new Add(new Num(1), new Num(2));! ! int sum = ast.match(new Matcher<Integer> {! @Override! public R matchNum(Num n) {! return n.value;! }! ! @Override! public R matchAdd(Add a) {! int left = a.left.match(this);! int right = a.right.match(this);! return left + right;! }! });
41. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java int ast = new Add(new Num(1), new Num(2));! ! int sum = ast.match(new Matcher<Integer> {! @Override! public Integer matchNum(Num n) {! return n.value;! }! ! @Override! public R matchAdd(Add a) {! int left = a.left.match(this);! int right = a.right.match(this);! return left + right;! }! });
42. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java int ast = new Add(new Num(1), new Num(2));! ! int sum = ast.match(new Matcher<Integer> {! @Override! public Integer matchNum(Num n) {! return n.value;! }! ! @Override! public Integer matchAdd(Add a) {! int left = a.left.match(this);! int right = a.right.match(this);! return left + right;! }! });
43. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Traversing an AST in Java public interface Node {! public <R> R match(Matcher<R> matcher);! }! ! public interface Matcher<R> {! public R matchNum(Num n);! public R matchAdd(Add a);! }
44. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro The Visitor Pattern public interface Node {! public <R> R visit(NodeVisitor<R> visitor);! }! ! public interface NodeVisitor<R> {! public R visitNum(Num n);! public R visitAdd(Add a);! }
45. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Nashorn $ nashorn: cd nashorn/src/jdk/nashorn/internal/ir/! $ ir: ls *Node.java! AccessNode.java FunctionNode.java ReturnNode.java! BaseNode.java IdentNode.java RuntimeNode.java! BinaryNode.java IfNode.java SplitNode.java! BreakNode.java IndexNode.java SwitchNode.java! BreakableNode.java LabelNode.java TernaryNode.java! CallNode.java LexicalContextNode.java ThrowNode.java! CaseNode.java LiteralNode.java TryNode.java! CatchNode.java LoopNode.java UnaryNode.java! ContinueNode.java Node.java VarNode.java! EmptyNode.java ObjectNode.java WhileNode.java! ForNode.java PropertyNode.java WithNode.java
46. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Nashorn $ ir: cd ..! $ internal: find . -name *Visitor*! ./ir/debug/PrintVisitor.java! ./ir/visitor/NodeOperatorVisitor.java! ./ir/visitor/NodeVisitor.java! $ internal: grep -hR 'extends NodeVisitor' .! final class FoldConstants extends NodeVisitor<LexicalContext> {! final class Splitter extends NodeVisitor<LexicalContext> {! public final class JSONWriter extends NodeVisitor<LexicalContext> {! public final class PrintVisitor extends NodeVisitor<LexicalContext> {! public class NodeOperatorVisitor<T extends LexicalContext> extends NodeVisitor<T> {
47. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Example Interpreter in Java https://github.com/igstan/tree-interpreter-visitor
48. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though: pattern matching ‣ The closest alternative is the Visitor pattern ‣ Cumbersome pattern, for me ‣ Last, but not least, I write Scala daily :-)
49. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though: pattern matching ‣ The closest alternative is the Visitor pattern ‣ Cumbersome pattern, for me ‣ Last, but not least, I write Scala daily :-)
50. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Why Scala ‣ I could have used Java 8 ‣ One missing feature, though: pattern matching ‣ The closest alternative is the Visitor pattern ‣ Cumbersome pattern, for me ‣ Last, but not least, I write Scala daily :-)
51. Ionuț G. Stan · ionut.g.stan@gmail.com · igstan.ro Coding Part