[Haskell-beginners] evaluation of expressions [was Re: eval command?]

[Brandon S. Allbery KF8NH]

On 2008 Oct 27, at 23:25, Andrew Sackville-West wrote:
> this raises a question for me, being a bit of a schemer. Is there any
> parallel in haskell to the data is code model of the lisp family? For
> example, playing around in scheme with a symbolic differentiator, it
> is trivial to then evaluate the differentiated s-expression at
> arbitrary value by representing the expression, and it's derivative as
> a regular scheme expression.
>
> Is this something that can be done in haskell? My initial impression
> is no, that you'd have to parse it as an expression and evaluate it as
> you would in regular imperative languages. I'd love to hear otherwise.


You get this in a type-safe form with Template Haskell; you can  
operate on expressions at the AST level.

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH