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/tactics/tacticals.ml b/tactics/tacticals.ml
index 664629f34..ae2307190 100644
--- a/tactics/tacticals.ml
+++ b/tactics/tacticals.ml
@@ -100,7 +100,7 @@ let onNLastHypsId n tac = onHyps (nLastHypsId n) tac
 let onNLastHyps n tac   = onHyps (nLastHyps n) tac
 
 let afterHyp id gl =
-  fst (List.split_when (Id.equal id % NamedDecl.get_id) (pf_hyps gl))
+  fst (List.split_when (NamedDecl.get_id %> Id.equal id) (pf_hyps gl))
 
 (***************************************)
 (*           Clause Tacticals          *)
@@ -593,7 +593,7 @@ module New = struct
   let afterHyp id tac =
     Proofview.Goal.enter { enter = begin fun gl ->
     let hyps = Proofview.Goal.hyps (Proofview.Goal.assume gl) in
-    let rem, _ = List.split_when (Id.equal id % NamedDecl.get_id) hyps in
+    let rem, _ = List.split_when (NamedDecl.get_id %> Id.equal id) hyps in
     tac rem
     end }