1. CS 614: Theory and Construction of Compilers
Lecture 11
Fall 2002
Department of Computer Science
University of Alabama
Joel Jones

2. Overview Action routines in Java Cup Abstract Syntax Trees
Readings for Next Time
©2002 Joel Jones

3. Action Routines in Java Cup
Associated with productions
Return Symbol
Symbol contains token type and value
Syntactically assign to RESULT with type of value
©2002 Joel Jones

4. Abstract Syntax Trees
Clean Interface between parser and later phases of compiler
Conveys phrase structure with all parsing issues resolved
©2002 Joel Jones

5. Concrete Syntax Vs. Abstract Syntax
Stm -> Stm ; Stm
Stm -> id := Exp
Stm -> print ( ExpList )
Exp -> id
Exp -> num
Exp -> Exp Binop Exp
Exp -> (Stm, Exp)
ExpList -> Exp, ExpList
ExpList -> Exp
BinOp -> + | - | * | /
S -> S ; S
S -> id := E
S -> print L
E -> id
E -> num
E -> E B E
E -> S , E
L ->
L -> L E
B -> + | - | * | /
©2002 Joel Jones

6. Representing Tree Data Structures in Java
A tree is described by one or more abstract classes, corresponding to a symbol in the grammar
Each abstract class is extended by one or more subclasses, one for each gramar rule
For each nontrivial symbol on rhs, thereis a field in the corresponding class
Each class has a constructor that initializes all fields and is thereafter immutable
©2002 Joel Jones

7. Readings for Next Time Chapter 4 through and including section 4.6
©2002 Joel Jones