On Sun, Jun 7, 2020 at 5:44 PM Ben Franksen wrote:

That said, he did write in one of his EWDs that beginners(!) should be tought programming with a language that does /not/ have an implementation available, in order to enourage thinking denotationally about programs rather than operationally, right from the start. The reason he preferred an imperative language for such a beginner's course (and also for communicating algorithms) is that recursion has a more complicated semantics (in terms of weakest preconditions) than his 'do' loop construct. This is important if, like Dijkstra did, you introduce every language construct by formally stating its denotational semantics, playing down the operational aspect as much as possible.

As a fun anecdote, Dijkstra's language referred to here, the Guarded Command Language, has actually seen several implementations despite his explicit intent for implementations never to exist: https://metacpan.org/pod/Commands::Guarded https://web.archive.org/web/20091214010836/http://www.dc.fi.udc.es/ai/~cabal... https://web.archive.org/web/20080622163307/http://gacela.labf.usb.ve/GacelaW... The last one there was actually used in the university I went to as the language for the first programming course for incoming CS students for the better part of a decade, until the department switched those courses to Python. Of note, also, is that 12 years passed from EWD1036 to his letter on using Haskell to teach introductory programming. I wonder if he ever wrote or shared his thoughts on whether this was merely a pragmatist's compromise, or a change of heart in light of Haskell's progress over those years: why did he not stick to GCL?

Haskell's reputation as a welcoming community is on shakier ground than it was a few years ago, and phrases like "despite your endless ranting" work against the collegial atmosphere we're proud of. No need to be faux polite, but when people (wrongly, in my opinion) describe us as an unwelcoming community, this is the type of convo I imagine them having come across and been scared off by. Tom El 7 jun 2020, a las 11:42, Ben Franksen escribió:

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Well, don't look for pointers to language design from the couple of jokers portrayed in that pdf.

I find it actually insulting to the good sense the real Dijkstra always showed; and insulting to Haskellers -- what's with all this gratuitous imputing of emotion? What's with just getting Haskell wrong? It's easy to check those claims; it's easy to get the (alleged) 'thought' peer-reviewed from the Haskell community.

Who is insulting and emotional here?

I really don't get why you're so upset about this harmless opinionated piece that, in a humorous and obviously exaggerated way, applies some of Dijkstra's ideas about programming language syntax to Haskell ("notational conventions" is just an informal synonym for syntax.) Putting these words into Dijkstra's mouth is just an artist's freedom, and in fact it gave me pause to think about the issues raised. (That was along time ago, BTW).

Despite your endless ranting the authors quite obviously do understand EWD1300. Their use of the word "first-class" may drive the rhetoric a bit over the top but that's pretty superficial IMO. The main point is that in a language like Haskell whitespace is overloaded: it can mean application or it can be a mere separator; which it is depends on the context. If Haskell /required/ the use of an explicit built-in infix operator for application then this context-dependency would disappear and white space would become only a separator. It is valid to argue that this would make the language esier to read. This has nothing to do with the fact that in Haskell you onbviously /can/ define infix application operator. (The argument about the type of application is bogus, though, I agree with you on that one.)

I also don't see how this has anything to do with Dijkstra promoting Haskell for teaching. In fact, I find it much less insulting to suggest that Dijkstra would have things to criticise about Haskell (he /was/ very much a perfectionist and if I can enumerate several shortcomings in Haskell off the top of my head, then so I guess he could have), than to suggest that this would be a reason for him to oppose using Haskell for teaching! I would venture that Dijkstra was realist enough to prefer something imperfect when it clearly trumps the competition.

That said, he did write in one of his EWDs that beginners(!) should be tought programming with a language that does /not/ have an implementation available, in order to enourage thinking denotationally about programs rather than operationally, right from the start. The reason he preferred an imperative language for such a beginner's course (and also for communicating algorithms) is that recursion has a more complicated semantics (in terms of weakest preconditions) than his 'do' loop construct. This is important if, like Dijkstra did, you introduce every language construct by formally stating its denotational semantics, playing down the operational aspect as much as possible.

Cheers Ben

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Sincere apologies if my message came across as me, personally, criticizing you(r actions), personally. Enforced 100% politeness isn't actually good for a community, and I have no special claim to an objective viewpoint on which messages are hurtful vs. harmful. Plus, I'm sure emails I've sent on this list have failed the test I'm describing now. On the other hand, almost certainly most people subscribed to the mailing list haven't read every email on the list, and even a message that's "justified frustration" in context can seem like a community full of jerks to people who don't have that full context. People (real people I've spoken to offline) worry their questions will be attacked or ridiculed, and so don't ask them and stay disengaged. Not the problem of one email or one author. And I certainly don't want to have to implicitly endorse (or not) whatever messages came before. The existence of other (imo) rude messages on the list underscores my point, not detracts from it. We should all try to make this place be and seem friendly. Tom

El 8 jun 2020, a las 11:49, Ben Franksen escribió:

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Am 08.06.20 um 16:07 schrieb amindfv@gmail.com: Haskell's reputation as a welcoming community is on shakier ground than it was a few years ago, and phrases like "despite your endless ranting" work against the collegial atmosphere we're proud of.

To put this in perspective, here are a few citations from what I have called "endless ranting":

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... misapplying ... in a rather badly-informed way. ... it doesn't seem to know Haskellers very well; nor Dijkstra's well-known support for Haskell in education. ... can't even spell his first name right... ... it's a couple of dudes shooting the breeze. ...To put it bluntly: the authors are blundering. ... a bogus problem; direct consequence of the authors not understanding EWD1300.

Do you regard this as "welcoming" language? If not, where was your concerned reply when they hit the list?

IMO the occasional ranting doesn't hurt anybody as long as it is addressed not to people but to technical shortcomings. However, the above citations are clearly ad-hominem attacks.

Or is your point that I directly addressed the author of the above lines, rather than attacking some third party?

Cheers Ben

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