Comments on: Revisiting Maybe in Java http://blog.tmorris.net/revisiting-maybe-in-java/ The weblog of Tony Morris Sat, 04 Feb 2012 12:42:40 +0000 http://wordpress.org/?v=2.6 By: Tony Morris http://blog.tmorris.net/revisiting-maybe-in-java/#comment-106009 Tony Morris Fri, 19 Aug 2011 00:12:36 +0000 http://blog.tmorris.net/revisiting-maybe-in-java/#comment-106009 G'day John, I haven't used C++ in quite a while, but I have seen representations in C++ which exploit the template system. There are quite a few people I know personally who have used C++ to such an extent, then discovered templates (which are turing-complete), then moved on to such things as Haskell or O'Caml, simply because it is an extension of the curiosity that they were already entertaining. Glad to help mate! G’day John,
I haven’t used C++ in quite a while, but I have seen representations in C++ which exploit the template system. There are quite a few people I know personally who have used C++ to such an extent, then discovered templates (which are turing-complete), then moved on to such things as Haskell or O’Caml, simply because it is an extension of the curiosity that they were already entertaining.

Glad to help mate!

]]> By: John http://blog.tmorris.net/revisiting-maybe-in-java/#comment-106003 John Thu, 18 Aug 2011 23:46:04 +0000 http://blog.tmorris.net/revisiting-maybe-in-java/#comment-106003 Hi Tony, I was reading your entire blog in the last weeks and I have to say it was very inspiring and I hope you keep on writing. I think to see the difference between IT and CS. I am just wondering to see many "comparisons" to Java. What about C++? Don't you have much experience with it? I suppose things like the maybe monad can be written in C++ in a much more elegant way than in Java and also the template system has more power than generics. Hi Tony,

I was reading your entire blog in the last weeks and I have to say it was very inspiring and I hope you keep on writing. I think to see the difference between IT and CS.

I am just wondering to see many “comparisons” to Java. What about C++? Don’t you have much experience with it? I suppose things like the maybe monad can be written in C++ in a much more elegant way than in Java and also the template system has more power than generics.

]]> By: λ Tony’s blog λ » Blog Archive » Maybe Monad in Java http://blog.tmorris.net/revisiting-maybe-in-java/#comment-30 λ Tony’s blog λ » Blog Archive » Maybe Monad in Java Mon, 18 Dec 2006 04:10:03 +0000 http://blog.tmorris.net/revisiting-maybe-in-java/#comment-30 [...] As I have shown previously, the problem of partial function in Java is not easily solved. The solution of the Maybe algebraic data type, while definitely superior to existing options, is cumbersome to implement and requires some functions defined over the type (isJust, isNothing, etc.) in order to be complete. As some point out, there is a preference for continuation passing to prevent the need for a cast (even though this case would be hidden). This prompted me to provide a more complete solution - which is still only a subset of a complete solution. [...] [...] As I have shown previously, the problem of partial function in Java is not easily solved. The solution of the Maybe algebraic data type, while definitely superior to existing options, is cumbersome to implement and requires some functions defined over the type (isJust, isNothing, etc.) in order to be complete. As some point out, there is a preference for continuation passing to prevent the need for a cast (even though this case would be hidden). This prompted me to provide a more complete solution - which is still only a subset of a complete solution. [...]

]]> By: Ricky Clarkson http://blog.tmorris.net/revisiting-maybe-in-java/#comment-29 Ricky Clarkson Thu, 16 Nov 2006 23:42:56 +0000 http://blog.tmorris.net/revisiting-maybe-in-java/#comment-29 Again with the [] for generics.. I think that you pass a NothingC[Q] to the maybe method instead of a Q directly to facilitate lazy evaluation. I went down this road with my functional stuff, and I found that I just didn't need it. It's simpler to be able to pass 5 to a method, rather than calling some wrapping, e.g., new NonNullNothingC[Integer](5). It is quite rare that I have a case where calculating that value is expensive. Of course, it happens, and that's when I choose laziness, but I don't have to force laziness on the rest of my code. I have a badly named interface, Returner, which is rather like your NothingC, and if I want laziness then I make the Function (Function is called JustC in your post) that I pass as the first parameter to accept (accept is called maybe in your post) return a Returner[Q] and make the second parameter a Returner[Q] also. This is quite rare, and usually indicates that I'm doing stuff with side-effects anyway, so I probably need a good old refactor. Implementing the Either type from Haskell is a nice exercise in Java too - again, done it already, although I called my accept method 'visit', stupidly.. http://functionalpeas.googlecode.com/svn/trunk/src/fpeas/either/ Again with the [] for generics..

I think that you pass a NothingC[Q] to the maybe method instead of a Q directly to facilitate lazy evaluation. I went down this road with my functional stuff, and I found that I just didn’t need it. It’s simpler to be able to pass 5 to a method, rather than calling some wrapping, e.g., new NonNullNothingC[Integer](5).

It is quite rare that I have a case where calculating that value is expensive. Of course, it happens, and that’s when I choose laziness, but I don’t have to force laziness on the rest of my code.

I have a badly named interface, Returner, which is rather like your NothingC, and if I want laziness then I make the Function (Function is called JustC in your post) that I pass as the first parameter to accept (accept is called maybe in your post) return a Returner[Q] and make the second parameter a Returner[Q] also.

This is quite rare, and usually indicates that I’m doing stuff with side-effects anyway, so I probably need a good old refactor.

Implementing the Either type from Haskell is a nice exercise in Java too - again, done it already, although I called my accept method ‘visit’, stupidly..

http://functionalpeas.googlecode.com/svn/trunk/src/fpeas/either/

]]>