PCCTS 1.30

                                    Announcing the 1.30 release of PCCTS


                                The Purdue Compiler Construction Tool Set


                                                        November 1, 1994


Items of note in versions since 1.30:


o Token references may now be labeled so that actions can refer to the
associated attributes with $label rather than $i for some integer
i. For example,


expr : NEGATE id:ID
<<printf("found -%s\n", $id->getText());>>
;


o A sophisticated error handling mechanism called PARSER EXCEPTION
HANDLING is now available (albeit, in alpha-quality
state)--providing a unified framework for reporting and recovering
from semantic and syntactic errors. While parser exception handling
has much in common with C++ exception handling, we do not actually
use C++ exceptions in our implementation; hence, parser exception
handling can be used with either the ANTLR C or C++ interface. For
example,


stat: "if" e:expr "then" stat { "else" stat }
exception[e]
catch MismatchedToken :
catch NoViableAlt :
<<
fprintf(stderr,
"line %d: if-stat: malformed conditional at \"%s\"\n",
line, LATEXT(1));
consumeUntilToken(THEN);
>>
| "while" expr "do" stat
...
;


The exception handler catches two predefined signals,
MismatchedToken and NoViableAlt, that occur during the recognition
of expr (by specifying a label on the rule reference and the
exception).


For input ``if 34+ then ...'', the parser would respond with


line 1: if-stat: malformed conditional at "then"


instead of the automatic mechanism's:


line 1: syntax error at "then" missing { INT FLOAT }.


for example.




For those users with anonymous FTP access, the main PCCTS site is:


                                  everest.ee.umn.edu (128.101.144.112)


in the directory:


                                  pub/pccts


Those with only email access, send:


                                  mail -s 'email install' pccts@ecn.purdue.edu
                                  mail -s 'email one.c' pccts@ecn.purdue.edu
                                  mail -s 'email pccts.bag' pccts@ecn.purdue.edu


If you are interested in sharing your experiences/problems/
successes/suggestions regarding PCCTS, please send join us
in the comp.compilers.tools.pccts newsgroup.


Thank you for your interest in PCCTS,


    The Authors of The Purdue Compiler Construction Tool Set:


    Terence J. Parr, parrt@acm.org
    Russell W. Quong quong@ecn.purdue.edu
    Will E. Cohen, cohenw@ecn.purdue.edu
    Henry G. Dietz, hankd@ecn.purdue.edu


Motto:


        "Why program by hand in 5 days what you can spend 5 years of your
          life automating?"
--

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