Comments on: Metalists for fun and profit http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/ Discussing modern C++ and related topics. Tue, 31 Jan 2012 01:36:14 +0000 hourly 1 http://wordpress.com/ By: rmn http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-304 Wed, 17 Feb 2010 19:23:37 +0000 http://cplusplus.co.il/?p=855#comment-304 It is perfectly possible to have Reduce result in a type instead of an int (or any other specific type). – This is left as an exercise :)

Indeed, if Reduce would result in a type then we could implement Map as a Reduce which executes a metafunction on every member and inserts its ‘output’ into the list which is its result. Very nice point!

]]> By: lorg http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-302 Mon, 15 Feb 2010 09:54:08 +0000 http://cplusplus.co.il/?p=855#comment-302 I beg to differ, see http://www.paulgraham.com/avg.html for example.

]]> By: haggai http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-291 Mon, 08 Feb 2010 15:16:22 +0000 http://cplusplus.co.il/?p=855#comment-291 Can you work with Reduce that outputs types other than int? Than you could implement Map using it.

]]> By: Manuel http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-286 Mon, 08 Feb 2010 08:12:53 +0000 http://cplusplus.co.il/?p=855#comment-286 nadavrot: Greate article, but maybe you could add a mention to [Boost Fusion lists](http://www.boost.org/doc/libs/1_41_0/libs/fusion/doc/html/fusion/container/list.html)? Seems pretty related to whay you present here…

]]> By: NN http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-285 Mon, 08 Feb 2010 07:52:22 +0000 http://cplusplus.co.il/?p=855#comment-285 Very well.
You have proved again that templates are Turing complete.

Anyway some useful idea.
It is better to follow Boost.MPL naming convention
( http://www.boost.org/doc/libs/1_42_0/libs/mpl/doc/index.html )
and to use the written classes instead of writing your own :)

E.g. there is boost::mpl::map too
http://www.boost.org/doc/libs/1_42_0/libs/mpl/doc/refmanual/map.html

]]> By: sulfide http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-283 Mon, 08 Feb 2010 00:11:08 +0000 http://cplusplus.co.il/?p=855#comment-283 cept no one really uses lisp in real projects

]]> By: lorg http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-282 Sun, 07 Feb 2010 22:42:40 +0000 http://cplusplus.co.il/?p=855#comment-282 I think you just proved Greenspun’s tenth rule again http://en.wikipedia.org/wiki/Greenspun%27s_Tenth_Rule :)

You could have also called your functions cons, car and cdr…

]]> By: Nadav http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-281 Sun, 07 Feb 2010 21:59:09 +0000 http://cplusplus.co.il/?p=855#comment-281 Thanks :) Next week we can do the one on PI and SIN.

]]> By: rmn http://cplusplus.co.il/2010/02/07/metalists-for-fun-and-profit/#comment-280 Sun, 07 Feb 2010 21:23:29 +0000 http://cplusplus.co.il/?p=855#comment-280 Great post Nadav! This is very similar to Alexandrescu’s Type Lists.

I wonder if anybody could come up with an even crazier use-case for this technique, perhaps something seen in a production code.

]]>