Re: [Haskell-cafe] Why monad tutorials don't work
On 14/08/07, Dan Weston [EMAIL PROTECTED] wrote: [snips another metaphor for monadic programming] No offence to Dan, whose post I enjoyed. The concept of wrapping is as close a metaphor as we seem to get without disagreements. But this has brought me to a realisation, after Paul Erdos: The Haskell community is a machine for converting coffee to monad tutorials. In the spirit of the venture, I will now suggest that someone points out that they don't like coffee, and that I haven't allowed for arrow tutorials ;-) Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why monad tutorials don't work
snark As you know, an arrow tutorial is like a wrapper around a monad tutorial, sort of like a container around it that can do extra actions with sufficient lifting. The appropriate higher-order function to convert monad tutorials to arrow tutorials will be left as an exercise to the reader. /snark I'm becoming more and more convinced that metaphors for monads do more harm than good. From now on I'm going to describe monads as purely abstract entities that obey certain laws, and that _in certain instances_ can be viewed to be like containers, or actions, or donuts, or whatever. In other words, a monad is an abstract thing that can generate things that we can metaphorize, but it's pointless (point-free?) to try to capture the entire concept in a single metaphor. I'm reminded of a physics teacher who was having a similar problem explaining the concept of tensors, until he said that a tensor is something that transforms like a tensor does!. So a monad is something that behaves like a monad does. Mike (who obviously hasn't had nearly enough coffee today) Dougal Stanton wrote: On 14/08/07, Dan Weston [EMAIL PROTECTED] wrote: [snips another metaphor for monadic programming] No offence to Dan, whose post I enjoyed. The concept of wrapping is as close a metaphor as we seem to get without disagreements. But this has brought me to a realisation, after Paul Erdos: The Haskell community is a machine for converting coffee to monad tutorials. In the spirit of the venture, I will now suggest that someone points out that they don't like coffee, and that I haven't allowed for arrow tutorials ;-) Cheers, D. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why monad tutorials don't work
On 8/14/07, Dan Weston [EMAIL PROTECTED] wrote: Conor McBride and Ross Paterson said it best in the introduction to their paper Applicative programming with effects [1]: As von Neumann said: Young man, in mathematics you don't understand things, you just get used to them. Getting used to something is, practically by definition, something that you can't do just by reading the ultimate tutorial. You just have to write the code, see the pattern happen again and again, and abstract it. There's no short cut. (Well...sometimes...) On 8/14/07, Michael Vanier [EMAIL PROTECTED] wrote: I'm reminded of a physics teacher who was having a similar problem explaining the concept of tensors, until he said that a tensor is something that transforms like a tensor does!. Grrr...must...hold...my...tongue... -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why monad tutorials don't work
On 8/14/07, Michael Vanier [EMAIL PROTECTED] wrote: I'm becoming more and more convinced that metaphors for monads do more harm than good. From now on I'm going to describe monads as purely abstract entities that obey certain laws, and that _in certain instances_ can be viewed to be like containers, or actions, or donuts, or whatever. In other words, a monad is an abstract thing that can generate things that we can metaphorize, but it's pointless (point-free?) to try to capture the entire concept in a single metaphor. I'm reminded of a physics teacher who was having a similar problem explaining the concept of tensors, until he said that a tensor is something that transforms like a tensor does!. So a monad is something that behaves like a monad does. Nice. As a Haskell beginner (with previous imperative programming experience) I subscribed to this list today to say exactly that. I spent weeks reading different tutorials that attempted to enlighten by means of various abstractions before I finally found one that simply showed the mechanics of the required operators and rules (sounds less formal than laws) that they need to hold to. Even then I hadn't quite got it until I met SPJ at OSCON and heard myself saying, All monads are are labels in front of values with specific operations defined on them. His reply was, Yes! Very abstract isn't it? Then I'd got it, or realized that I had but hadn't realized it (if that makes any sense...), as that sequential exchange of ideas (hah!) brought me to the realization that the abstractions that monads are held to represent are solely in the usage semantics of aforesaid operations and, while technically the actual labels used don't matter, we pick labels whose meaning match those semantics. So, yes, don't start by giving any extra meaning to the basic monad operations than their mechanics. Then show how they can be use to implement abstractions like state, uncertainty, etc... Oh yeah, start with terms that programmers already know, e.g. encapsulation v. wrappers. Then switch. Don't start with terminology that's different and explain the mappings, start with the familiar than follow the mappings to the different. -- Erik Jones [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why monad tutorials don't work
On Tue, 2007-08-14 at 16:02 -0700, Dan Piponi wrote: . . . On 8/14/07, Michael Vanier [EMAIL PROTECTED] wrote: I'm reminded of a physics teacher who was having a similar problem explaining the concept of tensors, until he said that a tensor is something that transforms like a tensor does!. Grrr...must...hold...my...tongue... Dan, as a former student of a clone of that physics teacher, I am really interested in what you will say when you fail to hold your tongue. -- Bill Wood ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
