🚀 go-pugleaf

To: lakshman@n.cs.uiuc.edu (T.K. Lakshman)
In-reply-to: lakshman@n.cs.uiuc.edu's message of 25 Feb 91 18:08:37 GMT
Subject: A Type checking/reconstruction procedure for Typed-Prolog
BCC: mattias
--text follows this line--
I like the type checker very much, it works fine under sicstus 0.7,
except that in the typechecker tries to redefine numbervars (are there
actually DEC-10 like prologs without numbervars?).

Thanks for posting a nice program!

/mattias


Two warnings to other users:

1) the program cannot handle disjunctions (anoying, but simple to fix,
just expand the disjunction to a set of clauses)

2) the program cannot distinguish between different predicates with
the same functor but different arity, e.g. foo/3 and foo/5. Rename
foo/5 to foo_aux/5.


Two suggestions/questions to the authors:

1) please redefine rload, so that it accepts a list of files, and
rewrite libdecls to fit your format (i.e. remove :- from the file).
then we can typecheck a set set of files, first loading libdecls, by
writing [libdelcs, file1, file2]. It doesn't bother me if all output
is put in the same file.

2) Funny (erroneous) behaviour:

the program

type bar --> a ; b.
type foo --> b ; c.

p(b).

results in

% Type Constructors    : 

type       bar(0).
type       foo(0).

% Types for Functions  : 

type       a:  []    -->     bar.
type       b:  []    -->     bar.
type       b:  []    -->     foo.
type       c:  []    -->     foo.

% Types for Predicates : 

pred       p(bar).

% Program   : 

             p(b).


but the program

type bar --> a ; b.
type foo --> b ; c.

p(b).
p(c).

results in an error

                                                                                           ...Reading declarations and program clauses 
 ... doing Type Checking / Reconstruction 

@#$%^&>> Type Conflict in types    fun([],foo)   and   fun(_2470,bar)
{ Execution aborted }
| ?- 


What behaviour is correct, both since the type declaration is
incorrect. The constant "b" occurs in several types.
--
Mattias Waldau                              
Computing Science Department                mattias@emil.csd.uu.se
P.O. Box 520, S-751 20  Uppsala, Sweden     Phone: +46-18-181055