It is based on https://developer.mbed.org/users/gregeric/code/Nucleo_Hello_Encoder/

Revision:
2:4580c3869b7b
Parent:
0:caf1d0bc4b90
--- a/rotary_encoder.cpp	Fri Feb 26 05:30:53 2016 +0000
+++ b/rotary_encoder.cpp	Fri Feb 26 16:08:52 2016 +0000
@@ -1,6 +1,8 @@
 #include "mbed.h"
 #include "rotary_encoder.hpp"
 
+namespace mbed_stl {
+
 const size_t rotary_encoder::max_counts_ = 0xFFFF;
 
 rotary_encoder::rotary_encoder(size_t resolution) :
@@ -10,3 +12,5 @@
 float rotary_encoder::get_revol_num() const {
     return static_cast<float>(get_counts()) / resolution_;
 }
+
+} /* namespace mbed_stl */