How about this? instance Show Process where show Stop = "Stop" show (Prefix l p) = concat ["(", l, "->", show p, ")"] show (External p q) = concat ["(", show p, " [] ", show q, ")"] Hope that helps, Bryn Andy Gimblett wrote:
A small stylistic question: what's the "best" way to build strings containing other values? For example, I have:
data Process = Stop | Prefix String Process | External Process Process
instance Show Process where show Stop = "Stop" show (Prefix l p) = "(" ++ l ++ "->" ++ show p ++ ")" show (External p q) = "(" ++ show p ++ " [] " ++ show q ++ ")"
but to me the extensive use of ++ is not particularly readable.
I'm very fond of Python's interpolation approach, where we'd have something like the following for the External case:
def __str__(self): return "(%s [] %s)" % (self.p, self.q)
which to me seems clearer, or at least easier to work out roughly what the string's going to look like. (The %s does an implicit "convert to string", btw).
Is there a facility like this in Haskell? Or something else I should be using, other than lots of ++ ?
Thanks,
-Andy