Re: Glasgow-haskell-users Digest, Vol 155, Issue 9

continuing my thought, There was a medical student, Jonathan, working here at True North. He was really into macrobiotics and studied with the great Denny Waxman. Jonathan told me legends of the great George Oshawa who traveled the world as a sort of super human meeting with people and inspiring and teaching people. One thing that really stuck with me is the note that this Oshawa would wake very early (maybe 3?) and spend hours writing letters. That sounds so nice!! I am remembering with gratitude a letter you wrote me in Japan. Best, Ralph On Sat, Jul 9, 2016 at 12:26 PM, Ralf Hutchison wrote:

Well Iavor likes it. (see 2 below)

Anyway, you know I'm really puzzled with the question of how to spend time.

Maybe you can help me.

In any case, it's such a lucky thing to have some to spend.

Toshia and I are watching season 4 of Game of Thrones. I'm so addicted.

I'm also addicted to speed chess in the same way. (I am ralf_ben_h at chess.com)

I think that we have some structure in our minds, in our brains or our spines or our hearts say, and any story or game illuminates and awakens this structure. The addictive feeling or attachment is a fascination with this part of ourselves and a willingness to experience it.

You wrote me a note about music recently. How are you feeling about music today?

Best, Ralph

On Sat, Jul 9, 2016 at 2:36 AM,

...

wrote:

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Today's Topics:

1. layout was Re: Proposal: ArgumentDo (C Maeder) 2. Re: Proposal: ArgumentDo (Iavor Diatchki) 3. Re: Proposal: ArgumentDo (C Maeder) 4. Re: Proposal: ArgumentDo (Bardur Arantsson) 5. Re: Proposal: ArgumentDo (Henrik Nilsson)

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Message: 1 Date: Fri, 8 Jul 2016 14:37:04 +0200 From: C Maeder To: glasgow-haskell-users@haskell.org Subject: layout was Re: Proposal: ArgumentDo Message-ID: <577F9E70.5090300@web.de> Content-Type: text/plain; charset=utf-8

Hi,

the layout language options are hard to find (at least in the user guide). Therefore I try to give an overview here. The relevant options I've found by using ghc-7.10.3 with option --supported-languages are:

NondecreasingIndentation DoAndIfThenElse

RelaxedLayout AlternativeLayoutRule AlternativeLayoutRuleTransitional

I ignore the last 3 options since these seem to be candidates for removal: https://ghc.haskell.org/trac/ghc/ticket/11359.

The default option is NondecreasingIndentation, that is

do x do y

is legal and parsed as a single expression "do {x ; do y}". With -XNoNondecreasingIndentation one gets an "Empty 'do' block" for the second do (and this error would not change with ArgumentDo!).

DoAndIfThenElse is not switched on by default and requires the keywords "then" and "else" to be further indented for an "if" within a "do".

So I believe these options do not interfere with ArgumentDo, but maybe this should be discussed more and maybe mentioned on the wiki page.

Surely a single space (inserted before x or removed before the second "do") makes a difference between one or two argument expressions in the example below.

HTH Christian

Am 08.07.2016 um 11:20 schrieb C Maeder:

...

Surely layout can bite you:

f do x do y

and I'm having difficulties to find the documentation for the various layout options.

But this is no argument against this proposal!

Improper use of white spaces can always be used to obfuscate code! Style guides are important. Furthermore, a wrong/unintended parse tree (due to layout) will - in many cases - result in a typing error.

Christian

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Message: 2 Date: Fri, 8 Jul 2016 09:42:24 -0700 From: Iavor Diatchki To: Aloïs Cochard Cc: GHC users , Henrik Nilsson Subject: Re: Proposal: ArgumentDo Message-ID: Content-Type: text/plain; charset="utf-8"

Hello,

while we are voting here, I kind of like this proposal, so +1 for me.

I understand that some of the examples look strange to Haskell old-timers but, as Joachim points out, the behavior is very consistent. Besides, the "Less Obvious Examples" were selected so that they are, well, less obvious. The common use cases (as in ticket #10843) seem quite appealing, at least to me, and not at all confusing. But, then, I also like the records-with-no-parens notation :-)

-Iavor

On Fri, Jul 8, 2016 at 5:03 AM, Aloïs Cochard wrote:

...

-1 for same reasons.

On 8 July 2016 at 14:00, Henrik Nilsson < Henrik.Nilsson@nottingham.ac.uk> wrote:

...

Hi all,

Joachim Breitner wrote:

...

Am Freitag, den 08.07.2016, 13:09 +0200 schrieb Sven Panne:

...

I don't think so: https://ghc.haskell.org/trac/ghc /wiki/ArgumentDo#Bl [...] Where is the outer set of parenthesis coming from?

This is all not related to the ArgumentDo notation. Note that [...]

The very fact that that experts can't easily agree on how a small Haskell fragment is parsed to me just confirms that Haskell already is a syntactically very cumbersome language.

The present proposal just makes matters worse. For that reason alone, I don't find it compelling at all. (So -1 from me, then.)

I will not repeat the many other strong arguments against that has been made. But I must say I don't find the use cases as documented on the associated web page compelling at all. Maybe there is a tacit desire to be able to pretend functions are keywords for various creative uses in supporting EDSLs and such. But for that to be truly useful, one need to support groups of related keywords. Something like Agda's mixfix syntax springs to mind. But this proposal does not come close, so the benefits are minimal and the drawbacks large.

As a final point, the inherent asymmetry of the proposal (the last argument position is special as, for certain kinds of expressions, parentheses may be omitted there but not elsewhere) is also deeply unsettling.

Best,

/Henrik

-- Henrik Nilsson School of Computer Science The University of Nottingham nhn@cs.nott.ac.uk

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