From cee495cac80ac9b778530943115a3172128ebf8a Mon Sep 17 00:00:00 2001
From: Sam Yates <halfflat@gmail.com>
Date: Fri, 28 Oct 2016 11:09:30 +0200
Subject: [PATCH] Address PR#46 review comments.
* Add documentation of template parameters for `filter_iterator`.
* Document use of `uninitalized<F>` for holding functional objects
in `filter_iterator` and `transform_iterator`
---
src/util/filter.hpp | 19 ++++++++++++++++++-
src/util/transform.hpp | 5 ++++-
2 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/src/util/filter.hpp b/src/util/filter.hpp
index 5fcbd1fd..6da37f57 100644
--- a/src/util/filter.hpp
+++ b/src/util/filter.hpp
@@ -32,12 +32,29 @@ namespace impl {
};
}
+/*
+ * Iterate through a sequence such that dereference only
+ * gives items from the range that satisfy a given predicate.
+ *
+ * Type parameters:
+ * I Iterator type
+ * S Sentinel type compatible with I
+ * F Functional object
+ *
+ * The underlying sequence is described by an iterator of type
+ * I and a sentinel of type S. The predicate has type F.
+ */
+
template <typename I, typename S, typename F>
class filter_iterator {
mutable I inner_;
S end_;
mutable bool ok_;
- mutable uninitialized<F> f_; // always in initialized state post-construction
+
+ // F may be a lambda type, and thus non-copy assignable. The
+ // use of `uninitalized` allows us to work around this limitation;
+ // f_ will always be in an initalized state post-construction.
+ mutable uninitialized<F> f_;
void advance() const {
if (ok_) return;
diff --git a/src/util/transform.hpp b/src/util/transform.hpp
index ec86ea71..71c49e72 100644
--- a/src/util/transform.hpp
+++ b/src/util/transform.hpp
@@ -26,7 +26,10 @@ class transform_iterator: public iterator_adaptor<transform_iterator<I, F>, I> {
friend class iterator_adaptor<transform_iterator<I, F>, I>;
I inner_;
- uninitialized<F> f_; // always in initialized state post-construction
+
+ // F may be a lambda type, and thus non-copy assignable. The
+ // use of `uninitalized` allows us to work around this limitation;
+ uninitialized<F> f_;
// provides access to inner iterator for adaptor.
const I& inner() const { return inner_; }
--
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