From 16a3540ea4257a19b9bfd9d5300a280e18b423a1 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 15 May 2019 20:48:20 -0700
Subject: [PATCH] [algs] Add hb_bind0 and hb_bind1

---
 src/hb-algs.hh   | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/test-algs.cc |  7 +++++++
 2 files changed, 61 insertions(+)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index f10e27939..17296e17e 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -119,6 +119,60 @@ struct
 }
 HB_FUNCOBJ (hb_invoke);
 
+enum class hb_bind_pos_t
+{
+  _0,
+  _1,
+};
+template <typename Appl, hb_bind_pos_t P, typename V>
+struct hb_binder_t
+{
+  hb_binder_t (Appl a, V v) : a (a), v (v) {}
+
+  template <typename ...Ts,
+	    hb_bind_pos_t PP = P,
+	    hb_enable_if (PP == hb_bind_pos_t::_0)> auto
+  operator () (Ts&& ...ds) -> decltype (hb_invoke (hb_declval (Appl),
+						   hb_declval (V),
+						   hb_declval (Ts)...))
+  {
+    return hb_invoke (hb_forward<Appl> (a),
+		      hb_forward<V> (v),
+		      hb_forward<Ts> (ds)...);
+  }
+  template <typename T0, typename ...Ts,
+	    hb_bind_pos_t PP = P,
+	    hb_enable_if (PP == hb_bind_pos_t::_1)> auto
+  operator () (T0&& d0, Ts&& ...ds) -> decltype (hb_invoke (hb_declval (Appl),
+							    hb_declval (T0),
+							    hb_declval (V),
+							    hb_declval (Ts)...))
+  {
+    return hb_invoke (hb_forward<Appl> (a),
+		      hb_forward<T0> (d0),
+		      hb_forward<V> (v),
+		      hb_forward<Ts> (ds)...);
+  }
+
+  private:
+  hb_reference_wrapper<Appl> a;
+  V v;
+};
+struct
+{
+  template <typename Appl, typename V> auto
+  operator () (Appl&& a, V&& v) const HB_AUTO_RETURN
+  (( hb_binder_t<Appl, hb_bind_pos_t::_0, V> (a, v) ))
+}
+HB_FUNCOBJ (hb_bind0);
+struct
+{
+  template <typename Appl, typename V> auto
+  operator () (Appl&& a, V&& v) const HB_AUTO_RETURN
+  (( hb_binder_t<Appl, hb_bind_pos_t::_1, V> (a, v) ))
+}
+HB_FUNCOBJ (hb_bind1);
+
 struct
 {
   private:
diff --git a/src/test-algs.cc b/src/test-algs.cc
index c4610d9e7..de96bde14 100644
--- a/src/test-algs.cc
+++ b/src/test-algs.cc
@@ -77,5 +77,12 @@ main (int argc, char **argv)
   xp = hb_pair_t<int *, double> (nullptr, 1);
   xp = hb_pair_t<const int*, int> (nullptr, 1);
 
+  assert (3 == hb_bind0 (hb_min, 3) (4));
+  assert (3 == hb_bind0 (hb_min, 4) (3));
+
+  auto M0 = hb_bind1 (hb_max, 0);
+  assert (M0 (-2) == 0);
+  assert (M0 (+2) == 2);
+
   return 0;
 }