From 6e91cb7cdb0c4f000a79d20d8578890d56bcdc84 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 22 Jan 2021 08:39:10 +0200
Subject: Add support for optional pair halves in variable values

---
 libbuild2/variable.ixx | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'libbuild2/variable.ixx')

diff --git a/libbuild2/variable.ixx b/libbuild2/variable.ixx
index c8f9541..9b24b9d 100644
--- a/libbuild2/variable.ixx
+++ b/libbuild2/variable.ixx
@@ -728,6 +728,31 @@ namespace build2
                  : s);
   }
 
+  // optional<T>
+  //
+  template <typename T>
+  inline int value_traits<optional<T>>::
+  compare (const optional<T>& l, const optional<T>& r)
+  {
+    return l
+      ? (r ? value_traits<T>::compare (*l, *r) : 1)
+      : (r ? -1 : 0);
+  }
+
+  // pair<F, S> value
+  //
+  template <typename F, typename S>
+  inline int value_traits<pair<F, S>>::
+  compare (const pair<F, S>& l, const pair<F, S>& r)
+  {
+    int i (value_traits<F>::compare (l.first, r.first));
+
+    if (i == 0)
+      i = value_traits<S>::compare (l.second, r.second);
+
+    return i;
+  }
+
   // vector<T> value
   //
   template <typename T>
-- 
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