From ade2363e357db3ac3f258e645fe6bba988e7e7dd Mon Sep 17 00:00:00 2001
From: Hugo Herbelin
Date: Thu, 19 Nov 2015 22:49:25 +0100
Subject: About building of substitutions from instances.

Redefining adjust_subst_to_rel_context from instantiate_context who
was hidden in inductiveops.ml, renamed the latter into
subst_of_rel_context_instance and moving them to Vars. The new name
highlights that the input is an instance (as for applist) and the
output a substitution (as for substl). This is a clearer unified
interface, centralizing the difficult de-Bruijn job in one place. It
saves a couple of List.rev.
---
 kernel/vars.ml | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'kernel/vars.ml')

diff --git a/kernel/vars.ml b/kernel/vars.ml
index f8c0a65e64..a00c7036fb 100644
--- a/kernel/vars.ml
+++ b/kernel/vars.ml
@@ -164,6 +164,21 @@ let substnl_decl laml k r = map_rel_declaration (fun c -> substnl laml k c) r
 let substl_decl laml r = map_rel_declaration (fun c -> substnl laml 0 c) r
 let subst1_decl lam r = map_rel_declaration (fun c -> subst1 lam c) r
 
+(* Build a substitution from an instance, inserting missing let-ins *)
+
+let subst_of_rel_context_instance sign l =
+  let rec aux subst sign l =
+    match sign, l with
+    | (_,None,_)::sign', a::args' -> aux (a::subst) sign' args'
+    | (_,Some c,_)::sign', args' ->
+	aux (substl subst c :: subst) sign' args'
+    | [], [] -> subst
+    | _ -> Errors.anomaly (Pp.str "Instance and signature do not match")
+  in aux [] (List.rev sign) l
+
+let adjust_subst_to_rel_context sign l =
+  List.rev (subst_of_rel_context_instance sign l)
+
 (* (thin_val sigma) removes identity substitutions from sigma *)
 
 let rec thin_val = function
-- 
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