[Haskell-cafe] Best way to build strings?
xoltar at xoltar.org
Wed Jul 20 12:28:35 EDT 2005
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,
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
>Is there a facility like this in Haskell? Or something else I should
>be using, other than lots of ++ ?
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