Update identifiers grammar, add constant $, fix :, add placeholder _

src/lexer.mll

@@ -2,8 +2,8 @@
   open Parser
 }
 
-let var_id   = ['A'-'Z'] ['A'-'Z' '0'-'9']*
-let func_id  = ['a'-'z' '0'-'9' '_']+
+let var_id   = ['A'-'Z'] ['A'-'Z' '0'-'9' '_' '-']* '\''*
+let func_id  = ['a'-'z' '0'-'9'] ['a'-'z' 'A'-'Z' '0'-'9' '_' '-']* '\''* '?'?
 let space    = [' ' '\t']+
 let newline  = '\r' | '\n' | "\r\n"
 
@@ -12,6 +12,7 @@ rule read = parse
   | func_id  { SYM (Lexing.lexeme lexbuf) }
   | '\''     { comment lexbuf }
   | "'''"    { comments lexbuf }
+  | '_'      { PLACEHOLDER }
   | '['      { LEFT_BRACK }
   | ']'      { RIGHT_BRACK }
   | '('      { LEFT_PAR }
@@ -20,6 +21,7 @@ rule read = parse
   | '@'      { AT }
   | '+'      { PLUS }
   | '-'      { MINUS }
+  | '$'      { EMPTY_SYM }
   | ':'      { CONS }
   | ';'      { SEMICOLON }
   | space    { read lexbuf }

src/parser.mly

@@ -7,6 +7,8 @@
 %token CONS
 %token AT
 %token SEMICOLON
+%token PLACEHOLDER
+%token EMPTY_SYM
 %token EOF
 
 %right CONS
@@ -33,6 +35,8 @@ symbol:
 | f = SYM { (Stellar.Null, f) }
 
 ray:
+| EMPTY_SYM { Stellar.to_func ((Stellar.Null, "$"), []) }
+| PLACEHOLDER { Stellar.to_var ("_"^(Stellar.fresh_placeholder ())) }
 | x = VAR { Stellar.to_var x }
 | r1 = ray; CONS; r2 = ray { Stellar.to_func ((Stellar.Null, ":"), [r1; r2]) }
 | pf = symbol; LEFT_PAR; ts = separated_nonempty_list(COMMA?, ray); RIGHT_PAR

src/stellar.ml

@@ -31,6 +31,12 @@ open StellarRays
    Stars and Constellations
    --------------------------------------- *)
 
+let counter_placeholder = ref 0
+let fresh_placeholder () =
+  let r = !counter_placeholder in
+  (counter_placeholder := !counter_placeholder + 1);
+  (Int.to_string r)
+
 type ray = term
 type star = ray list
 type constellation = star list
@@ -58,17 +64,16 @@ let is_polarised r : bool =
   | (Null, _) -> false
   in exists_func aux r
 
-let is_prefixed ~by:_ : ray -> bool = function
-  | Func (_, _) -> true
-  | _ -> false
-
 (* ---------------------------------------
    Pretty Printer
    --------------------------------------- *)
 
 let rec string_of_ray = function
   | Var x -> x
   | Func (pf, []) -> string_of_polsym pf
+  | Func ((Null, ":"), [Func ((Null, ":"), [r1; r2]); r3]) ->
+    "(" ^ (string_of_ray r1) ^ ":"  ^ (string_of_ray r2) ^ "):" ^
+    (string_of_ray r3)
   | Func ((Null, ":"), [r1; r2]) ->
     (string_of_ray r1) ^ ":"  ^ (string_of_ray r2)
   | Func (pf, ts) -> string_of_polsym pf ^
@@ -199,11 +204,13 @@ let interaction ?(withloops=true) ?(showtrace=false) ?(selfint=false) cs space =
             output_string stdout "\n";
           end;
           let new_stars =
+            search_partners ~withloops ~showtrace (r, accr@s') (cs@space')
+            |>
             if selfint then
-              self_interaction ~withloops ~showtrace (r, accr@s') @
-              search_partners ~withloops ~showtrace (r, accr@s') cs
+              List.append (self_interaction ~withloops ~showtrace (r, accr@s')) 
             else
-              search_partners ~withloops ~showtrace (r, accr@s') cs in
+              Fn.id
+            in
           if List.is_empty new_stars then select_ray (r::accr) s'
           else Some new_stars
       in let new_stars = select_ray [] s in