The History of PCCTS

The Purdue Compiler-Construction Tool Set

Terence Parr

Parr Research Corporation

Minneapolis, Minnesota

and

University of Minnesota

Army High Performance Computing Research Center

[Updated 8-7-94]

The PCCTS project began as a parser-generator project for a gra-

duate course at Purdue University in the Fall of 1988 taught by Hank

Dietz- translator-writing systems. Under the guidance of Professor

Dietz, the parser generator, ANTLR (originally called YUCC), continued

after the termination of the course and eventually became the subject

of Terence Parr's Master's thesis. Originally, lexical analysis was

performed via ALX which was soon replaced by Will Cohen's DLG in the

Fall of 1989 (DFA-based lexical-analyzer generator, also an offshoot

of the graduate translation course).

The alpha version of ANTLR was totally rewritten resulting in

1.00B. Version 1.00B was released via an internet newsgroup

(comp.compilers) posting in February of 1990 and quickly gathered a

large following. 1.00B generated only LL(1) parsers, but allowed the

merged description of lexical and syntactic analysis. It had rudimen-

tary attribute handling similar to that of YACC and did not incor-

porate rule parameters or return values; downward inheritance was very

awkward. 1.00B-generated parsers terminated upon the first syntax

error. Lexical classes (modes) were not allowed and DLG did not have

an interactive mode.

Upon starting his Ph.D. at Purdue in the Fall of 1990, Terence

Parr began the second total rewrite of ANTLR. The method by which

grammars may be practically analyzed to generate LL(k) lookahead

information was discovered in August of 1990 just before his return.

Version 1.00 incorporated this algorithm and included the AST mechan-

ism, lexical classes, error classes, and automatic error recovery;

code quality and portability were higher. In February of 1992 1.00

was released via an article in SIGPLAN Notices. Peter Dahl, Ph.D.

candidate, and Professor Matt O'Keefe (both at the University of Min-

nesota) tested this version extensively. Dana Hoggatt (Micro Data

Base Systems, Inc.) came up with the idea of error grouping (strings

attached to non-terminals) and tested 1.00 heavily.

Version 1.06 was released in December 1992 and represented a

large feature enhancement over 1.00. For example, rudimentary seman-

tic predicates were introduced, error messages were significantly

improved for k>1 lookahead and ANTLR parsers could indicate that loo-

kahead fetches were to occur only when necessary for the parse

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(normally, the lookahead "pipe" was constantly full). Russell Quong

joined the project in the Spring of 1992 to aid in the semantic predi-

cate design. Beginning and advanced tutorials were created and

released as well. A makefile generator was included that sets up

dependencies and such correctly for ANTLR and DLG. Very few 1.00

incompatibilities were introduced (1.00 was quite different from 1.00B

in some areas).

1.10 was released on August 31, 1993 and incorporated bug fixes,

a few feature enhancements and a major new capability - an arbitrary

lookahead operator (syntactic predicate), (alpha)?beta. This feature

was co-designed with Professor Russell Quong also at Purdue. To sup-

port infinite lookahead, a preprocessor flag, ZZINF_LOOK, was created

that forced the ANTLR() macro to tokenize all input prior to parsing.

Hence, at any moment, an action or predicate can see the entire input

sentence. The predicate mechanism of 1.06 was extended to allow mul-

tiple predicates to be hoisted; the syntactic context of a predicate

was also moved along with the predicate.

In February of 1994, SORCERER (a simple tree-parser generator)

was released. This tool allows the user to parse child-sibling trees

by specifying a grammar rather than building a recursive-descent tree

walker by hand. Work towards a library of tree transformations is

underway. Aaron Sawdey at The University of Minnesota became a second

author of SORCERER after the initial release.

On April 1, 1994, PCCTS 1.20 was released. This was the first

version to actively support C++ output. It also included important

fixes regarding semantic predicates and (..)+ subrules. This version

also introduced token classes, the "not" operator, and token ranges.

On June 19, 1994, SORCERER 1.00B9 was released. Gary Funck of

Intrepid Technology joined the SORCERER team and provided very valu-

able suggestions regarding the "transform" mode of SORCERER.

On August 8, 1994, PCCTS 1.21 was released. It mainly cleaned up

the C++ output and included a number of bug fixes.

From the 1.21 release forward, the maintenance and support of all

PCCTS tools will be primarily provided by Parr Research Corporation,

Minneapolis MN---an organization founded on the principles of excel-

lence in research and integrity in business; we are devoted to provid-

ing really cool software tools. Please see file PCCTS.FUTURE for more

information. All PCCTS tools currently in the public domain will con-

tinue to be in the public domain.

Looking towards the future, a graphical user-interface is in the

design phase. This would allow users to view the syntax diagram

representation of their grammars and would highlight nondeterministic

productions. Parsing can be traced graphically as well. This system

will be built using a multiplatform window library. We also antici-

pate the introduction of a sophisticated error handling mechanism

called "parser exception handling" in a near future release.

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Currently, PCCTS is used at over 1000 known academic, government,

and commercial sites in 37 countries. Of course, the true number of

users is unknown due to the large number of ftp sites.

Credits

_____________________________________________________________________________

_____________________________________________________________________________

|ANTLR 1.00A Terence Parr Hank Dietz |

|ALX Terence Parr Hank Dietz |

|ANTLR 1.00B Terence Parr Hank Dietz, Will Cohen |

|DLG 1.00B Will Cohen Terence Parr, Hank Dietz |

|NFA Relabelling Will Cohen |

|LL(k) analysis Terence Parr Hank Dietz |

|ANTLR 1.00 Terence Parr Hank Dietz, Will Cohen |

|DLG 1.00 Will Cohen Terence Parr, Hank Dietz |

|ANTLR 1.06 Terence Parr Will Cohen, Russell Quong, Hank Dietz|

|DLG 1.06 Will Cohen Terence Parr, Hank Dietz |

|ANTLR 1.10 Terence Parr Will Cohen, Russell Quong |

|ANTLR 1.20 Terence Parr Will Cohen, Russell Quong |

|ANTLR 1.21 Terence Parr Russell Quong |

|DLG 1.10 Will Cohen Terence Parr |

|DLG 1.20 Will Cohen Terence Parr |

|DLG 1.21 Terence Parr |

|Semantic predicates Terence Parr Russell Quonq |

|Syntactic predicates Terence Parr Russell Quonq |

|SORCERER 1.00A Terence Parr |

|SORCERER 1.00B Terence Parr Aaron Sawdey |

|SORCERER 1.00B9 Terence Parr Aaron Sawdey, Gary Funck |

|___________________________________________________________________________|

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