Added ProcessStream to for running processes (on Linux) and streaming their output.

Added map() function for creating a mapping iterator.
Added mijin::pipe types for map() and join().

source/mijin/util/string.hpp

@@ -47,6 +47,22 @@ std::string join(const TRange& elements, const char* const delimiter)
     return oss.str();
 }
 
+namespace pipe
+{
+struct Join
+{
+    const char* delimiter;
+
+    explicit Join(const char* delimiter_) noexcept : delimiter(delimiter_) {}
+};
+
+template<typename TIterable>
+auto operator|(TIterable&& iterable, const Join& joiner)
+{
+    return join(std::forward<TIterable>(iterable), joiner.delimiter);
+}
+}
+
 } // namespace mijin
 
 #endif // !defined(MIJIN_UTIL_STRING_HPP_INCLUDED)