main = getArgs >>= \args ->
if length args /= 1 || head args `notElem` known_args
- then error ("usage: genprimopcode command < primops.txt > ...\n"
+ then error ("usage: genprimopcode command < primops.i > ...\n"
++ " where command is one of\n"
++ unlines (map (" "++) known_args)
)