[amibroker] Better Bollinger Bands

[Dang Hoang Minh]

             In an article
in Futures Magazine, October 1998, Dennis McNicholl describesthe use of
Bollinger Bands and provides a means of making them tighter whenmarkets
are trending. He calls them Better Bollinger Bands.


             Here is the formula for MetaStock. Please help me convert to AFL 
Code. 

Better Bollinger Bands I
                          pds:=Input("Periods",2,200,20);

  sd:=Input("Standard Deviations",.01,10,2);

  alpha:=2/(pds+1);

  mt:=alpha*C+(1-alpha)*(If(Cum(1)<pds,C,PREV));

  ut:=alpha*mt+(1-alpha)*(If(Cum(1)<pds,C,PREV));

  dt:=((2-alpha)*mt-ut)/(1-alpha);

  mt2:=alpha*Abs(C-dt)+(1-alpha)*PREV;

  ut2:=alpha*mt2+(1-alpha)*PREV;

  dt2:=((2-alpha)*mt2-ut2)/(1-alpha);

  but:=dt+sd*dt2;

  blt:=dt-sd*dt2;

  dt;

  but;

  blt
Better Bollinger Bands II
                          Lb:=Input("Look-Back Period ?",3,100,20);

  De:=Input("Band Deviation ?",.5,3,2);

  Alp:=2/(Lb+1);

  Mt:=Alp*CLOSE+(1-Alp)*PREV;

  Ut:=Alp*Mt+(1-Alp)*PREV;

  Dt:=((2-Alp)*Mt-Ut)/(1-Alp);

  mt2:=Alp*Abs(C-Dt)+(1-Alp)*PREV;

  ut2:=Alp*mt2+(1-alp)*PREV;

  dt2:=((2-Alp)*mt2-ut2)/(1-Alp);

  But:=Dt+de*dt2;

  Blt:=Dt-de*dt2;

  But;

  Dt;

  Blt;