[Haskell-cafe] Re: QuickCheck: Arbitrary for a complex type
stefanor at cox.net
Wed Apr 4 18:13:09 EDT 2007
On Wed, Apr 04, 2007 at 10:59:45PM +0100, Joel Reymont wrote:
> One last bit then...
> My identifiers should start with letter <|> char '_' and the tail
> should be alphaNum <|> char '_'.
> I guess I can use choose and oneof to produce the right set of
> characters but how do I combine the two into a single identifier of
> a given length (up to 20 chars, say)?
> Thanks, Joel
> On Apr 4, 2007, at 5:27 PM, Fawzi Mohamed wrote:
> >Great, just one thing that could be important : when you have
> >recursive structures (like your Statement through Compound) be sure
> >to use
> >sized (\mySize -> ...)
> >as generator for arbitrary so that you can avoid infinite looping.
quickcheck is a monad so you can just do:
do first <- elements $ '_' : ['a' .. 'z']
len <- elements $ [5..19]
rest <- replicateM len $ elements $ '_' : ['a' .. 'z'] ++ ['0' .. '9']
return (first : rest)
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