DEFINITION MODULE MASREP;

(* MAS Representation Definition Module. *)

FROM MASSTOR IMPORT LIST;


PROCEDURE NewRep(): LIST;
(*New representation. A new representation is returned. *)


PROCEDURE SetRep(n,e,r: LIST);
(*Set representation. r is a representation. n is a unique 
label, e is an expression. *)


PROCEDURE GetRep(n,r: LIST): LIST;
(*Get representation. r is a representation. n is a unique 
label, An expression e stored under n is returned. *)


PROCEDURE CopyRep(r: LIST): LIST;
(*Copy representation. r is a representation. A copy of r is 
returned. Step counters are reset. *)


PROCEDURE StepRep(r: LIST): LIST;
(*Step through representation. r is a representation. 
The next expression e and its label n are returned as pair (n,e). 
If all pairs (n,e) of representation r have been processed, 
then NIL is returned. *)


PROCEDURE ForEachinRep(r, f, E: LIST): LIST;
(*For each pair (n,e) in r apply function f. r is a representation. 
(n, e) is a pair in r, where e is an expression and n is its label.
f is applied to (n, e) such that p = f(n,e) with p = (n', e') or p = NIL. 
If p <> NIL, then the pair (n', e') is added to the returned 
representation r' = { n' e' : f(n,e) <> NIL, n e in r }. E is a 
LISP environment, if E = NIL, then the top level environment is used. *)


PROCEDURE FullRep(r: LIST): LIST;
(*Full representation. Test for non-empty representation.
r is a representation. *)


PROCEDURE ForEachinList(r, f, E: LIST): LIST;
(*For each element e in r apply function f. r is a list. e is an 
element in r. f is applied to e such that e' = f(e). 
E is a LISP environment, if E = NIL, then the top level environment 
is used. *)

END MASREP.