Availability:C-language interface function
void PL_WITH_ENGINE(PL_engine_t 
e)This macro implements a C for-loop where the body is executed 
with the engine e as current engine. The body is executed 
exactly once. After completion of the body the current engine of the 
calling thread is restored to old state (either the old current engine 
or no engine). The user may use break to terminate the body 
early. The user may not use return. Using return 
does not reset the old engine.