[Haskell-cafe] Best way to build strings?

[Frank-Andre Riess]

Hello there,

> 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)

are you familiar with C's printf procedure? It's where that kind of notation 
comes from.
You can use Text.Printf which provides the function

printf :: PrintfType r => String -> r

Thus you can write

show (Prefix l p) = printf "(%s->%s)" l q
show (External p q) = printf "(%s [] %s)" p q

Alas, I couldn't test it, because the Text module seems to not be installed on 
my computer (sad thing not being the admin, isn't it?)
Nevertheless, take a look at
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Text.Printf.html

Regards,
Frank-Andre Riess