From 4f21c45748816c9e0cd4f93fa6f6d167e9757f81 Mon Sep 17 00:00:00 2001
From: Matej Kosik
Date: Tue, 30 Aug 2016 11:47:35 +0200
Subject: 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).
---
 proofs/goal.ml    | 2 +-
 proofs/tacmach.ml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

(limited to 'proofs')

diff --git a/proofs/goal.ml b/proofs/goal.ml
index 75f56c6b9d..a141708c2b 100644
--- a/proofs/goal.ml
+++ b/proofs/goal.ml
@@ -78,7 +78,7 @@ module V82 = struct
     let evars = Sigma.to_evar_map evars in
     let evars = Evd.restore_future_goals evars prev_future_goals prev_principal_goal in
     let ctxt = Environ.named_context_of_val hyps in
-    let inst = Array.map_of_list (mkVar % NamedDecl.get_id) ctxt in
+    let inst = Array.map_of_list (NamedDecl.get_id %> mkVar) ctxt in
     let ev = Term.mkEvar (evk,inst) in
     (evk, ev, evars)
 
diff --git a/proofs/tacmach.ml b/proofs/tacmach.ml
index e900240761..93e276f4ba 100644
--- a/proofs/tacmach.ml
+++ b/proofs/tacmach.ml
@@ -103,7 +103,7 @@ let pf_const_value              = pf_reduce (fun env _ -> constant_value_in env)
 let pf_reduce_to_quantified_ind = pf_reduce reduce_to_quantified_ind
 let pf_reduce_to_atomic_ind     = pf_reduce reduce_to_atomic_ind
 
-let pf_hnf_type_of gls          = pf_whd_all gls % pf_get_type_of gls
+let pf_hnf_type_of gls          = pf_get_type_of gls %> pf_whd_all gls
 
 let pf_is_matching              = pf_apply Constr_matching.is_matching_conv
 let pf_matches                  = pf_apply Constr_matching.matches_conv
-- 
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