Please write a Maple procedure called Position which retures the position i of an element x in a list L

That is, Position should return an integer i>0 such that L[i]=x. If x is not in list L,0 is returned..

i found command i may need to use 

proc(), do end do ,member(e, a,'p'), if then elif, end proc, 

can anyone help with this？  it may be a too elementary question to ask here .....and i know

 beginner