#pragma once
-/*
- * Iterim macros (until we have C++0x range-based for) that simplify
- * writing loops of the form
- *
- * for (Container<data>::iterator i = c.begin(); i != c.end(); ++i) statement
- *
- * Just replace the above with:
- *
- * FOR_EACH (i, c) statement
- *
- * and everything is taken care of.
+/**
+ * This header is deprecated
*
- * The implementation is a bit convoluted to make sure the container is
- * evaluated only once (however, keep in mind that c.end() is evaluated
- * at every pass through the loop). To ensure the container is not
- * evaluated multiple times, the macro defines one do-nothing if
- * statement to inject the Boolean variable FOR_EACH_state1, and then a
- * for statement that is executed only once, which defines the variable
- * FOR_EACH_state2 holding an rvalue reference to the container being
- * iterated. The workhorse is the last loop, which uses the just-defined
- * rvalue reference FOR_EACH_state2.
+ * Use range-based for loops, and if necessary Ranges-v3.
*
- * The state variables are nested so they don't interfere; you can use
- * FOR_EACH multiple times in the same scope, either at the same level or
- * nested.
+ * Some of the messaging here presumes that you have coded:
*
- * In optimized builds g++ eliminates the extra gymnastics entirely and
- * generates code 100% identical to the handwritten loop.
+ * #include <range/v3/all.hpp>
+ * using namespace ranges;
*/
-#include <type_traits>
#include <folly/Preprocessor.h>
+#include <type_traits>
/*
* Form a local variable name from "FOR_EACH_" x __LINE__, so that
#define _FE_ANON(x) FB_CONCATENATE(FOR_EACH_, FB_CONCATENATE(x, __LINE__))
/*
- * Shorthand for:
- * for (auto i = c.begin(); i != c.end(); ++i)
- * except that c is evaluated only once.
+ * If you just want the element values, please use:
+ *
+ * for (auto&& element : collection)
+ *
+ * If you need access to the iterators please write an explicit iterator loop
*/
#define FOR_EACH(i, c) \
if (bool _FE_ANON(s1_) = false) {} else \
i != _FE_ANON(s2_).end(); ++i)
/*
- * Similar to FOR_EACH, but iterates the container backwards by
- * using rbegin() and rend().
+ * If you just want the element values, please use this (ranges-v3) construct:
+ *
+ * for (auto&& element : collection | view::reverse)
+ *
+ * If you need access to the iterators please write an explicit iterator loop
*/
#define FOR_EACH_R(i, c) \
if (bool _FE_ANON(s1_) = false) {} else \
i != _FE_ANON(s2_).rend(); ++i)
/*
- * Similar to FOR_EACH but also allows client to specify a 'count' variable
- * to track the current iteration in the loop (starting at zero).
- * Similar to python's enumerate() function. For example:
- * string commaSeparatedValues = "VALUES: ";
- * FOR_EACH_ENUMERATE(ii, value, columns) { // don't want comma at the end!
- * commaSeparatedValues += (ii == 0) ? *value : string(",") + *value;
- * }
+ * If you just want the element values, please use this (ranges-v3) construct:
+ *
+ * for (auto&& element : collection | view::zip(view::ints))
+ *
+ * If you need access to the iterators please write an explicit iterator loop
+ * and use a counter variable
*/
#define FOR_EACH_ENUMERATE(count, i, c) \
if (bool _FE_ANON(s1_) = false) {} else \
if (const size_t& count = _FE_ANON(n1_)) {} else \
for (auto i = FOR_EACH_state2.begin(); \
i != FOR_EACH_state2.end(); ++_FE_ANON(n1_), ++i)
-
/**
- * Similar to FOR_EACH, but gives the user the key and value for each entry in
- * the container, instead of just the iterator to the entry. For example:
- * map<string, string> testMap;
- * FOR_EACH_KV(key, value, testMap) {
- * cout << key << " " << value;
- * }
+ * If you just want the keys, please use this (ranges-v3) construct:
+ *
+ * for (auto&& element : collection | view::keys)
+ *
+ * If you just want the values, please use this (ranges-v3) construct:
+ *
+ * for (auto&& element : collection | view::values)
+ *
+ * If you need to see both, use:
+ *
+ * for (auto&& element : collection) {
+ * auto const& key = element.first;
+ * auto& value = element.second;
+ * ......
+ * }
+ *
*/
#define FOR_EACH_KV(k, v, c) \
if (unsigned int _FE_ANON(s1_) = 0) {} else \
} }
/*
- * Iteration with given limits. end is assumed to be reachable from
- * begin. end is evaluated every pass through the loop.
+ * Look at the Ranges-v3 views and you'll probably find an easier way to build
+ * the view you want but the equivalent is roughly:
*
- * NOTE: The type of the loop variable should be the common type of "begin"
- * and "end". e.g. If "begin" is "int" but "end" is "long", we want "i"
- * to be "long". This is done by getting the type of (true ? begin : end)
+ * for (auto& element : make_iterator_range(begin, end))
*/
#define FOR_EACH_RANGE(i, begin, end) \
for (auto i = (true ? (begin) : (end)); \
++i)
/*
- * Iteration with given limits. begin is assumed to be reachable from
- * end by successive decrements. begin is evaluated every pass through
- * the loop.
+ * Look at the Ranges-v3 views and you'll probably find an easier way to build
+ * the view you want but the equivalent is roughly:
*
- * NOTE: The type of the loop variable should be the common type of "begin"
- * and "end". e.g. If "begin" is "int" but "end" is "long", we want "i"
- * to be "long". This is done by getting the type of (false ? begin : end)
+ * for (auto& element : make_iterator_range(begin, end) | view::reverse)
*/
#define FOR_EACH_RANGE_R(i, begin, end) \
for (auto i = (false ? (begin) : (end)); ::folly::detail::downTo(i, (begin));)