sql server - passing unquoted constants to functions like DATEPART does

Question

i would like to create a function which accepts a constant like the datepart function accepts yy/mm/dd/hh/

like:

select datepart(

Answer 1

i would like to create my own function that accepts dd not char like 'dd'

I think you're out of luck on this. If you don't single-quote the characters, they'll be interpreted as a name--but you can't have defined them as a name anywhere if you want them to be used in the manner you propose.