diff -r da1f8c033b8e -r 94f5cce73a4f progs/parser-combinators/comb2.sc
--- a/progs/parser-combinators/comb2.sc	Thu Sep 19 19:25:13 2024 +0100
+++ b/progs/parser-combinators/comb2.sc	Sun Sep 29 18:46:02 2024 +0100
@@ -14,12 +14,12 @@
 // case x ~ y ~ z => ...
 
 
-case class ~[+A, +B](x: A, y: B)
+case class o[+A, +B](x: A, y: B)
 
 
-type IsSeq[I] = I => Seq[_]
+type IsSeq[I] = I => Seq[?]
 
-abstract class Parser[I, T](using is: I => Seq[_])  {
+abstract class Parser[I, T](using is: I => Seq[?])  {
   def parse(in: I): Set[(T, I)]  
 
   def parse_all(in: I) : Set[T] =
@@ -37,10 +37,10 @@
 
 // sequence parser
 class SeqParser[I : IsSeq, T, S](p: => Parser[I, T], 
-                                 q: => Parser[I, S]) extends Parser[I, ~[T, S]] {
+                                 q: => Parser[I, S]) extends Parser[I, o[T, S]] {
   def parse(in: I) = 
     for ((hd1, tl1) <- p.parse(in); 
-         (hd2, tl2) <- q.parse(tl1)) yield (new ~(hd1, hd2), tl2)
+         (hd2, tl2) <- q.parse(tl1)) yield (new o(hd1, hd2), tl2)
 }
 
 // map parser
@@ -87,13 +87,13 @@
 // p"<_some_string_>" 
 
 extension (sc: StringContext) 
-  def p(args: Any*) = StrParser(sc.s(args:_*))
+  def p(args: Any*) = StrParser(sc.s(args*))
 
 
 // more convenient syntax for parser combinators
 extension [I : IsSeq, T](p: Parser[I, T]) {
   def ||(q : => Parser[I, T]) = new AltParser[I, T](p, q)
-  def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q)
+  def o[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q)
   def map[S](f: => T => S) = new MapParser[I, T, S](p, f)
 }
 
@@ -124,13 +124,13 @@
 
 // arithmetic expressions
 lazy val AExp: Parser[String, AExp] = 
-  (Te ~ p"+" ~ AExp).map[AExp]{ case x ~ _ ~ z => Aop("+", x, z) } ||
-  (Te ~ p"-" ~ AExp).map[AExp]{ case x ~ _ ~ z => Aop("-", x, z) } || Te
+  (Te o p"+" o AExp).map[AExp]{ case x o _ o z => Aop("+", x, z): AExp } ||
+  (Te o p"-" o AExp).map[AExp]{ case x o _ o z => Aop("-", x, z) } || Te
 lazy val Te: Parser[String, AExp] = 
-  (Fa ~ p"*" ~ Te).map[AExp]{ case x ~ _ ~ z => Aop("*", x, z) } || 
-  (Fa ~ p"/" ~ Te).map[AExp]{ case x ~ _ ~ z => Aop("/", x, z) } || Fa  
+  (Fa o p"*" o Te).map[AExp]{ case x o _ o z => Aop("*", x, z) } || 
+  (Fa o p"/" o Te).map[AExp]{ case x o _ o z => Aop("/", x, z) } || Fa  
 lazy val Fa: Parser[String, AExp] = 
-   (p"(" ~ AExp ~ p")").map{ case _ ~ y ~ _ => y } || 
+   (p"(" o AExp o p")").map{ case _ o y o _ => y } || 
    IdParser.map(Var(_)) || 
    NumParser.map(Num(_))