Amibroker code for Exp. Mov. Avge? (or convert formula from Metastock to Amibroker?)

Does anyone know the full AFL code to create a custom EMA?



Alternatively, if somone could help me convert the following Metastock formula, it would be most appreciated!



Pds:= 200;



Rate:=2 / (Pds+1);



M:=If(Cum(1)=1, C, PREV*(1-Rate) + C*Rate );



ValueWhen(1,Cum(1)>=Pds,M);