Re: [Haskell-cafe] quoting in Haskell
On 8/27/07, Peter Verswyvelen [EMAIL PROTECTED] wrote: In Scheme, on can quote code, so that it becomes data. Microsoft's F# and C# 3.0 also have something similar that turns code into expression trees. The latter is used extensively in LINQ which translates plain C# code into SQL code or any other code at runtime (this idea came from FP I heared) I can't find something similar for Haskell? Maybe I am looking at the wrong places? In Haskell, I know one can use a data constructor as a function (as in (map Just [1..3])), but a function cannot be turned into a data constructor (= quoting), can it? Now this is all really fuzzy for a newbie like me, because aren't all functions initially just data constructors waiting to be evaluated in a lazy language? I'm actually looking for something like (loose terminilogy follows) context-based-semi-quoting. The idea is to only quote a set of functions, while evaluating all the others. For example, in the code 1 `add` 2 `mul` 3 where add = (+) mul = (*) I want to write something like selectiveQuote [add] (1 `add` 2 `mul` 3) which would result in an expression tree like add / \ 16 So the `mul` is not quoted because it is not part of the context = [add] Maybe this is just impossible, I did not dig deep into this. Thanks, Peter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe Look at Template Haskell. quote from http://haskell.org/th : Intuitively Template Haskell provides new language features that allow us to convert back and forth between concrete syntax, i.e. what you would type when you write normal Haskell code, and abstract syntax trees. These abstract syntax trees are represented using Haskell datatypes and, at compile time, they can be manipulated by Haskell code. This allows you to reify (convert from concrete syntax to an abstract syntax tree) some code, transform it and splice it back in (convert back again), or even to produce completely new code and splice that in, while the compiler is compiling your module. However I don't know if your 'selectiveQuote' is possible using TH. regards, Bas van Dijk ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] quoting in Haskell
Look at Template Haskell. Intuitively Template Haskell provides new language features that allow us to convert back and forth between concrete syntax, i.e. what Gee coming from C++ that was the last thing I expected templates to do. It seems a bit more powerful in Haskell though! I'll look into that! Thanks, Peter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] quoting in Haskell
On Mon, 2007-08-27 at 17:56 +0200, Peter Verswyvelen wrote: Look at Template Haskell. Intuitively Template Haskell provides new language features that allow us to convert back and forth between concrete syntax, i.e. what Gee coming from C++ that was the last thing I expected templates to do. It seems a bit more powerful in Haskell though! I'll look into that! They aren't related to templates in C++ at all. It follows from the general meaning of the word template (as does C++'s usage). Really, it's not all that appropriate a name anyway. You may also find Liskell interesting http://liskell.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] quoting in Haskell
On 8/27/07, Derek Elkins [EMAIL PROTECTED] wrote: ...Really, it's not all that appropriate a name anyway... Indeed, Meta Haskell would be better I think. Bas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] quoting in Haskell
On 8/27/07, Peter Verswyvelen [EMAIL PROTECTED] wrote: Look at Template Haskell. Gee coming from C++ that was the last thing I expected templates to do. It seems a bit more powerful in Haskell though! There's much in common between C++ template metaprogramming and template Haskell - they both allow compile-time computation. On the question of which is more 'powerful', check out the side by side comparison here: http://www.cs.rice.edu/~taha/publications/journal/dspg04b.pdf -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] quoting in Haskell
At Mon, 27 Aug 2007 17:04:17 +0200, Peter Verswyvelen wrote: In Scheme, on can quote code, so that it becomes data. Microsoft's F# and C# 3.0 also have something similar that turns code into expression trees. The latter is used extensively in LINQ which translates plain C# code into SQL code or any other code at runtime (this idea came from FP I heared) Depending on what you are trying to do, you might also be able to use some of the DSL techniques that Lennart Augustsson has been exploring in his blog over the past couple months. This is probably a good starting point: http://augustss.blogspot.com/2007_06_01_archive.html j. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
