Hi all, Manuel Gómez wrote:
Further, it is also worth noting that by almost any measure C++ is an extremely successful language despite its warts.
Ah, success at the cost of warts. I see our priorities as a community have changed.
That's nonsensical and unnecessarily polemic. I am merely pointing out that removal of every single "wart" is not a prerequisite for success. But striving for "perfection" can have significant and even unjustifiable costs.
`return` should have never been a part of the `Monad` type class.
That's an odd statement. The mathematical concept of a monad clearly does not necessitate structuring things as a hierarchy of classes. In any case, the point is that "return" has been part of "Monad" for some 25 years. That's a serious historical legacy that should not be dismissed lightly for reasons already discussed.
In a post-AMP Haskell, however, retaining `return` in `Monad` does not serve any purpose:
That is not true. It does provide for an opportunity to write code that works with versions of GHC prior to 7.10 as well as later versions with a few fairly small fixes and (without resorting to conditional compilation). That's important to some people.
This community rightly values statically eliminating opportunities for errors, and the removal of `return` as a method of `Monad` serves this purpose. This is reason alone to implement this proposal, even in the absence of `ApplicativeDo`.
While I do accept your point about a mostly redundant "return" providing one opportunity to accidentally breaking a law that should hold, *any* Monad instance provide an opportunity for breaking multiple laws. Further, there are a range of classes where there are methods with default instances that are there to provide for an opportunity for more efficient implementation. They also need to satisfy laws and again there is an opportunity for accidentally breaking those. I am thus hard pressed to believe that keeping "return" as a method makes of Monad makes any perceptible practical difference either way in that respect. So, at least in my opinion, this is argument is no stronger than those already put forward. All the best, /Henrik -- Henrik Nilsson School of Computer Science The University of Nottingham nhn@cs.nott.ac.uk This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system, you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.