1 files changed, 61 insertions, 5 deletions
diff --git a/src/compat/iter.hpp b/src/compat/iter.hpp
index 7793d90..ff146a0 100644
--- a/src/compat/iter.hpp
+++ b/src/compat/iter.hpp
@@ -1,5 +1,4 @@
-#ifndef TMWA_COMPAT_ITER_HPP
-#define TMWA_COMPAT_ITER_HPP
+#pragma once
 //    iter.hpp - tools for dealing with iterators
 //
 //    Copyright © 2012-2014 Ben Longbons <b.r.longbons@gmail.com>
@@ -19,11 +18,13 @@
 //    You should have received a copy of the GNU General Public License
 //    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# include "../sanity.hpp"
+#include "fwd.hpp"
 
-# include <iterator>
+#include <iterator>
 
 
+namespace tmwa
+{
 /// Simple class to use a pair of iterators with foreach
 template<class It>
 class IteratorPair
@@ -94,4 +95,59 @@ IteratorPair<ValueIterator<T>> value_range(T b, T e)
     return {b, e};
 }
 
-#endif // TMWA_COMPAT_ITER_HPP
+
+template<class T, class F, class C>
+class FilterIterator
+{
+    F filter;
+    C *container;
+
+    using InnerIterator = decltype(std::begin(*container));
+    InnerIterator impl;
+public:
+    void post_adv()
+    {
+        while (impl != std::end(*container))
+        {
+            if (filter(*impl))
+                break;
+            ++impl;
+        }
+    }
+
+    FilterIterator(C *c, F f)
+    : filter(f), container(c), impl(std::begin(*c))
+    {
+        post_adv();
+    }
+
+    void operator ++()
+    {
+        ++impl;
+        post_adv();
+    }
+
+    T operator *()
+    {
+        return *impl;
+    }
+
+    friend
+    bool operator != (FilterIterator l, FilterIterator)
+    {
+        return l.impl != std::end(*l.container);
+    }
+};
+
+template<class T>
+bool is_truthy(T v)
+{
+    return v;
+}
+
+template<class T, class F=decltype(is_truthy<T>)*, class C>
+IteratorPair<FilterIterator<T, F, C>> filter_iterator(C *c, F f=is_truthy<T>)
+{
+    return {FilterIterator<T, F, C>(c, f), FilterIterator<T, F, C>(c, f)};
+}
+} // namespace tmwa