refactoring ...

[helm.git] / helm / software / helena / src / basic_rg / brg.ml

diff --git a/helm/software/helena/src/basic_rg/brg.ml b/helm/software/helena/src/basic_rg/brg.ml
new file mode 100644 (file)
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+++ b/helm/software/helena/src/basic_rg/brg.ml
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+(*
+    ||M||  This file is part of HELM, an Hypertextual, Electronic        
+    ||A||  Library of Mathematics, developed at the Computer Science     
+    ||T||  Department, University of Bologna, Italy.                     
+    ||I||                                                                
+    ||T||  HELM is free software; you can redistribute it and/or         
+    ||A||  modify it under the terms of the GNU General Public License   
+    \   /  version 2 or (at your option) any later version.              
+     \ /   This software is distributed as is, NO WARRANTY.              
+      V_______________________________________________________________ *)
+
+(* kernel version: basic, relative, global *)
+(* note          : ufficial basic lambda-delta *) 
+
+module E = Entity
+module N = Level
+
+type uri = E.uri
+type attrs = E.attrs
+
+type bind = Void                   (*             *)
+          | Abst of N.level * term (* level, type *)
+          | Abbr of term           (* body        *)
+
+and term = Sort of attrs * int         (* attrs, hierarchy index *)
+         | LRef of attrs * int         (* attrs, position index *)
+         | GRef of attrs * uri         (* attrs, reference *)
+         | Cast of attrs * term * term (* attrs, type, term *)
+         | Appl of attrs * term * term (* attrs, argument, function *)
+         | Bind of attrs * bind * term (* attrs, binder, scope *)
+
+type entity = term E.entity (* attrs, uri, binder *)
+
+type lenv = Null
+(* Cons: tail, relative local environment, attrs, binder *) 
+          | Cons of lenv * lenv * attrs * bind 
+
+(* Currified constructors ***************************************************)
+
+let abst n w = Abst (n, w)
+
+let abbr v = Abbr v
+
+let lref a i = LRef (a, i)
+
+let cast a u t = Cast (a, u, t)
+
+let appl a u t = Appl (a, u, t)
+
+let bind a b t = Bind (a, b, t)
+
+let bind_abst n a u t = Bind (a, Abst (n, u), t)
+
+let bind_abbr a v t = Bind (a, Abbr v, t)
+
+let bind_void a t = Bind (a, Void, t)
+
+(* local environment handling functions *************************************)
+
+let empty = Null
+
+let push e c a b = Cons (e, c, a, b)
+
+let rec get i = function
+   | Null                         -> Null, Null, [], Void
+   | Cons (e, c, a, b) when i = 0 -> e, c, a, b
+   | Cons (e, _, _, _)            -> get (pred i) e
+
+let get e i = get i e
+
+(* used in BrgOutput.pp_lenv *)
+let rec fold_right f map e x = match e with   
+   | Null              -> f x
+   | Cons (e, c, a, b) -> fold_right (map f e c a b) map e x