Hi,
can you define the output data type in a custom function; I thought , seemingly wrongly, you put it outside the brackets,
so 

 (x ) as number  => 
let
timer = x * 10 
in 
 timer
when used as an addcolumn the new column would be type number? it's not, so can it be done and what does a data type out side of hte function
mean ? ( x as type ) as type =>

Richard.