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, 1 insertions, 1 deletions

diff --git a/ltac/rewrite.ml b/ltac/rewrite.ml
index ad052cdd1d..09454f3e83 100644
--- a/ltac/rewrite.ml
+++ b/ltac/rewrite.ml
@@ -1540,7 +1540,7 @@ let assert_replacing id newt tac =
     let concl = Proofview.Goal.concl gl in
     let env = Proofview.Goal.env gl in
     let ctx = Environ.named_context env in
-    let after, before = List.split_when (Id.equal id % NamedDecl.get_id) ctx in
+    let after, before = List.split_when (NamedDecl.get_id %> Id.equal id) ctx in
     let nc = match before with
     | [] -> assert false
     | d :: rem -> insert_dependent env (LocalAssum (NamedDecl.get_id d, newt)) [] after @ rem