[Haskell-cafe] Haskell - string to list isusses, and more

[Luke Palmer]

On Mon, Jun 15, 2009 at 3:03 AM, Luke Palmer <lrpalmer at gmail.com> wrote:

>
> The last thing: we made startsWithUpper less general in the process; it is
> undefined for empty strings.  We need to verify that words never returns any
> empty strings.  I did this using SmallCheck:
>
> ghci> import Test.SmallCheck
> ghci> smallCheck 10 $ \string -> all (not . null) (words string)
>

'Course, it turns out that SmallCheck never generates any spaces... ever.
Some verifier that is.

By careful inspection of the definition of words, I can see that it never
returns an empty string.  I couldn't find a better way to convince myself of
this (I like to avoid looking at definitions when possible).

Luke



> Depth 0:
>   Completed 1 test(s) without failure.
> Depth 1:
>   Completed 2 test(s) without failure.
> Depth 2:
>   Completed 5 test(s) without failure.
> Depth 3:
>   Completed 16 test(s) without failure.
> Depth 4:
>   Completed 65 test(s) without failure.
> Depth 5:
>   Completed 326 test(s) without failure.
> Depth 6:
>   Completed 1957 test(s) without failure.
> Depth 7:
>   Completed 13700 test(s) without failure.
> Depth 8:
>   Completed 109601 test(s) without failure.
> Depth 9:
>   Completed 986410 test(s) without failure.
> Depth 10:
>   Completed 9864101 test(s) without failure.
>
> So I am reasonably confident that words never gives me any empty strings.
>
> Tada!  Your solution is almost exactly the same as the one-liners! :-)
>
> Luke
>
>
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