CLEANUP: switching from "right-to-left" to "left-to-right" function composition operator.

Short story:

    This pull-request:

    (1) removes the definition of the "right-to-left" function composition operator

    (2) adds the definition of the "left-to-right" function composition operator

    (3) rewrites the code relying on "right-to-left" function composition to rely on "left-to-right" function composition operator instead.

Long story:

    In mathematics, function composition is traditionally denoted with ∘ operator.

    Ocaml standard library does not provide analogous operator under any name.

    Batteries Included provides provides two alternatives:

    	_ % _

    and

    	_ %> _

    The first operator one corresponds to the classical ∘ operator routinely used in mathematics.
    I.e.:

    	(f4 % f3 % f2 % f1) x  ≜  (f4 ∘ f3 ∘ f2 ∘ f1) x

    We can call it "right-to-left" composition because:
    - the function we write as first (f4) will be called as last
    - and the function write as last (f1) will be called as first.

    The meaning of the second operator is this:

    	(f1 %> f2 %> f3 %> f4) x  ≜  (f4 ∘ f3 ∘ f2 ∘ f1) x

    We can call it "left-to-right" composition because:
    - the function we write as first (f1) will be called first
    - and the function we write as last (f4) will be called last
    That is, the functions are written in the same order in which we write and read them.

    I think that it makes sense to prefer the "left-to-right" variant because
    it enables us to write functions in the same order in which they will be actually called
    and it thus better fits our culture
    (we read/write from left to right).

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/term_typing.ml b/kernel/term_typing.ml
index 8db65e33c9..7a5ac7a39c 100644
--- a/kernel/term_typing.ml
+++ b/kernel/term_typing.ml
@@ -262,7 +262,7 @@ let record_aux env s_ty s_bo suggested_expr =
     String.concat " "
       (CList.map_filter (fun decl ->
           let id = NamedDecl.get_id decl in
-          if List.exists (Id.equal id % NamedDecl.get_id) in_ty then None
+          if List.exists (NamedDecl.get_id %> Id.equal id) in_ty then None
           else Some (Id.to_string id))
         (keep_hyps env s_bo)) in
   Aux_file.record_in_aux "context_used" (v ^ ";" ^ suggested_expr)
@@ -285,7 +285,7 @@ let build_constant_declaration kn env (def,typ,proj,poly,univs,inline_code,ctx)
   let sort evn l =
     List.filter (fun decl ->
       let id = NamedDecl.get_id decl in
-      List.exists (Names.Id.equal id % NamedDecl.get_id) l)
+      List.exists (NamedDecl.get_id %> Names.Id.equal id) l)
     (named_context env) in
   (* We try to postpone the computation of used section variables *)
   let hyps, def =