From ebf47a95f29dd959319feb7f8728f7c0162a181e Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 15 May 2019 15:14:26 -0700
Subject: [PATCH] [iter] Simplify operator!= of iterator filters

Both to save ops, and also because lambdas don't implement operator!=,
so this was failing in range-based for loop if a lambda was passed to
hb_map() or hb_filter().  Just check end-condition assuming that we
are comparing to .end() or iterators that are otherwise derived from
current iterator.  Ie. don't compare things that are expected to be
in common.
---
 src/hb-iter.hh | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/hb-iter.hh b/src/hb-iter.hh
index 140e55365..5df433375 100644
--- a/src/hb-iter.hh
+++ b/src/hb-iter.hh
@@ -378,7 +378,7 @@ struct hb_map_iter_t :
   void __rewind__ (unsigned n) { it -= n; }
   hb_map_iter_t __end__ () const { return hb_map_iter_t (it.end (), f); }
   bool operator != (const hb_map_iter_t& o) const
-  { return it != o.it || f != o.f; }
+  { return it != o.it; }
 
   private:
   Iter it;
@@ -441,7 +441,7 @@ struct hb_filter_iter_t :
   void __prev__ () { do --it; while (it && !hb_has (p.get (), hb_get (f.get (), *it))); }
   hb_filter_iter_t __end__ () const { return hb_filter_iter_t (it.end (), p, f); }
   bool operator != (const hb_filter_iter_t& o) const
-  { return it != o.it || p != o.p || f != o.f; }
+  { return it != o.it; }
 
   private:
   Iter it;
@@ -553,6 +553,8 @@ struct hb_zip_iter_t :
   void __prev__ () { --a; --b; }
   void __rewind__ (unsigned n) { a -= n; b -= n; }
   hb_zip_iter_t __end__ () const { return hb_zip_iter_t (a.end (), b.end ()); }
+  /* Note, we should stop if ANY of the iters reaches end.  As such two compare
+   * unequal if both items are unequal, NOT if either is unequal. */
   bool operator != (const hb_zip_iter_t& o) const
   { return a != o.a && b != o.b; }
 
@@ -621,7 +623,7 @@ struct hb_counter_iter_t :
   void __rewind__ (unsigned n) { v -= n * step; }
   hb_counter_iter_t __end__ () const { return hb_counter_iter_t (end_, end_, step); }
   bool operator != (const hb_counter_iter_t& o) const
-  { return v != o.v || end_ != o.end_ || step != o.step; }
+  { return v != o.v; }
 
   private:
   static inline T end_for (T start, T end_, S step)