need help converting old style def fn functions

[madscijr]

Hi
very strange code

DEF FNB(Q)=Q+8*((Q=9)-(Q=0))
this function returns Q for all value of Q except for 9 that returns 1  and  for 0 that returns 8
Is it better using an IF THEN ELSEIF THEN ELSE  that seems less cryptic!

and this other
DEF FNC(Q)=-Q*(Q<19)-18*(Q>18)
it returns Q + 18 if Q>18  or -Q if Q<19

moreover
DEF FND(Q)=64*(Q-1)+8*(X-1)+Y
translated in Function must get X and Y to do a correct calculation
Dim Shared  versus Function parameters

and at last
DEF FNE(Q)=Q+100*(Q>99) 
this FN returns Q if Q <=99  and it returns Q-100 for Q value > 99

However creativity is the first tool of a programmer|

Indeed. 
I think this may have been created waaay back in the day, maybe in GW-BASIC or BASIC A?