Continue massaging Ostap

stdlib/Expr.expr

@@ -2,25 +2,48 @@ import Ostap;
 import List;
 import Fun;
 
+public fun left (f) {
+  fun (c, x) {
+     fun (y) {
+       f (c (x), y)
+     }
+  }
+}
+
+public fun right (f) {
+  fun (c, x) {
+    fun (y) {
+      c (f (x, y))
+    }
+  }
+}
+
 --- ops -> fun (x, y) {x `op` y}
-fun altl (ps) {
-  case ps of
-    p : ps -> foldl (infix |, p, ps)
+fun altl (level) {
+  case level of
+    [assoc, ps] ->
+       case map (fun (p) {
+                   case p of
+                     [op, sema] -> op @ lift(assoc (sema))
+                   esac
+                 }, ps) of
+         p : ps -> foldl (infix |, p, ps)
+       esac
   esac
 }
 
 public fun expr (ops, opnd) {
   fun inner (ops) {
     case ops of
-      {}         -> opnd
+      {}         -> fun (c) {opnd @ c}
     | level : tl ->
         local lops = altl (level),
               next = inner (tl);
         
-        fun this (k) {
-           next |> fun (l) {lops |> fun (op) {this @ fun (r) {op (l, r)}}}
-         | next
-         $ k
+        fun this (c) {
+           next (id) |> fun (l) {lops |> fun (op) {this (op (c, l))}}
+         | next (id) @ c
+         -- $ k
         }
 
         this