+ config.interpolate(prev_config, next_config, \
+ (next_position == prev_position) ? \
+ get_source_position() : prev_position, \
+ (next_position == prev_position) ? \
+ get_source_position() + 1 : next_position, \
+ get_source_position()); \
+ } \
+ return !config.equivalent(old_config) ? 1 : 0; \