CS 614: Theory and Construction of Compilers

Lecture 9

Fall 2002

Department of Computer Science

University of Alabama

Joel Jones

©2002 Joel Jones

Outline

“Everybody Dance One More Time” Finish problem from last class

Introduction to Java Cup Reading & Questions for Next Class

©2002 Joel Jones

Definitions

P

L

M

S T

L

S

L

Program P expressed in language L

Machine M

Translator from S to T expressed in L

Interpreter for S expressed in language L

©2002 Joel Jones

More Tombstone Diagram Problems 3: (Gnu RTL intermediate language; HLL: C, C+

+, Pascal; Machine Code: Alpha, PPC, SPARC; RTL->RTL optimizer; all written in C Install on SPARC, given a C compiler for SPARC Compile P in Pascal, into SPARC machine code Compile using RTL optimizer Cross-compile C++ program Q for PPC machine

code

©2002 Joel Jones

Quick Diagnostic

Pair Up:

• What is a finite automata (finite state machine)?

• What are its components?

©2002 Joel Jones

Fundamental of LALR Parsing Bottom-up

Unlike recursive-descent which is top-down Model is finite-automata with a stack

The parsers state represents what is expected next in the input

Transition to next state based upon the top of the stack, next (1) input symbol, and current state

Stack contains symbols, both terminals and nonterminals

On transition, stack may pushed (shift), popped (reduce), or unchanged (epsilon)

©2002 Joel Jones

Purpose of Parser Generator

Translate a specification of a grammar into a parser

Most parser generators are for Context-free Grammars (CFG) and produce LALR(1) or LL(1) parsers

Grammar specification is annotated with action routines that are executed when a reduction is made

©2002 Joel Jones

Java Cup

Accepts specification of a CFG and produces an LALR(1) parser (expressed in Java) with action routines expressed in Java

Similar to yacc in its specification language, but with a few improvements (better name management)

©2002 Joel Jones

java_cup_spec ::= package_spec import_list code_part init_code scan_code symbol_list precedence_list start_spec

production_list

Java Cup Specification Structure

Great, but what does it mean? Package and import controls Java naming Code and init_code allows insertion of code in generated output Scan code specifies how scanner (lexer) is invoked Symbol list and precedence list specify terminal and non-

terminal names and their precedence Start and production specify grammar and its start point

©2002 Joel Jones

Example Java Cup Specification (partial)

import java_cup.runtime.*;

/* Terminals (tokens returned by the scanner). */terminal SEMI, PLUS, MINUS, TIMES, DIVIDE, MOD;terminal Integer NUMBER;

/* Non terminals */non terminal expr_list, expr_part;

/* Precedences */precedence left PLUS, MINUS;

/* The grammar */expr_list ::= expr_list expr_part | expr_part;

©2002 Joel Jones

Running Java Cup Manually Download and build Java Cup

export CLASSPATH=~/src/java_cup_v10k ./INSTALL

Run Java Cup on the specification java Java_cup Main Arith.y -or- java_cup Arith.y

Run Jlex on scanner specification jlex Number.l

Build parser and scanner javac parser.java javac Number.l.java

(cont.)

©2002 Joel Jones

Running Java Cup Manually (cont.) Build driver program

java ParseDemo.java

Run driver program java ParseDemo << EOF

©2002 Joel Jones

Reading & Questions for Next Class Java Cup Web page

http://www.cs.princeton.edu/~appel/modern/java/CUP/