From mboxrd@z Thu Jan  1 00:00:00 1970
From: Federico Beffa <beffa@ieee.org>
Subject: bug#21829: guix import hackage failures
Date: Thu, 26 Nov 2015 09:28:07 +0100
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To: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Cc: 21829@debbugs.gnu.org

On Wed, Nov 25, 2015 at 10:45 PM, Ludovic Court=C3=A8s <ludo@gnu.org> wrote=
:
> Federico Beffa <beffa@ieee.org> skribis:

[...]

>>>> +      ;; indentation based block recognition.
>>>> +      (begin (unread-char #\newline port) (read-char port) 0)
>>>
>>> Isn=E2=80=99t this equivalent to: 0 ?
>>
>> No. This is because at the start of a new line we check if and how
>> many indentation blocks have ended. If the last line doesn't terminate
>> this check is no done.
>
> More generally, it looks like:
>
>   (begin (do-effect!) (undo-effect!) val)
>
> which I thought reduces to:
>
>   val

Since we are doing IO, there are side effects. The key difference is
the result of '(port-column port)' and that triggers what I mentioned.

Thanks for the review.
Regards,
Fede