Add more CTL content

ctl/is_sorted.h

@@ -0,0 +1,25 @@
+// -*-mode:c++;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8-*-
+// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
+#ifndef CTL_IS_SORTED_H_
+#define CTL_IS_SORTED_H_
+
+namespace ctl {
+
+template<typename It, typename Compare>
+bool
+is_sorted(It first, It last, Compare comp)
+{
+    if (first == last)
+        return true;
+    It next = first;
+    while (++next != last) {
+        if (comp(*next, *first))
+            return false;
+        first = next;
+    }
+    return true;
+}
+
+} // namespace ctl
+
+#endif // CTL_IS_SORTED_H_