[NTG-context] Some macros (Metafun)

Hello, In the Metafun manual, Hans uses macros like drawpath p ; drawcontrollines p ; drawpoints p ; drawcontrolpoints p ... How to use them in a document ? Where to find source codes ? For example, the following code does not work : \starttext \startuseMPgraphic{path} path p ; p := (1cm,1cm)--(1.5cm,1.5cm)..(2cm,0cm)..cycle ; \stopuseMPgraphic \startMPcode p := p .. cycle ; swappointlabels := true ; drawpath p ; \stopMPcode \stoptext Thank you Fabrice