Smerl breakthough: metacurrying

Yariv Sadan <>
Mon Aug 21 04:59:30 CEST 2006


Fascinating stuff, David. Thanks for the link. I only know Lisp on a
basic level and although I know Lisp has great metaprogramming
capabilities I didn't know about this specific feature. I guess I have
some homework to do :)

Best,
Yariv


On 8/19/06, David Hopwood <> wrote:
> Yariv Sadan wrote:
> > Hi,
> >
> > I added a new capability to Smerl, allowing you to curry parameters
> > for function forms in runtime, finally freeing us from having to know
> > the Erlang abstract form!
> >
> [...]
> > http://yarivsblog.com/articles/2006/08/19/erlang-metaprogramming-breakthrough-metacurrying
>
> This functionality is similar to Lisp's quasiquoting. It is generalized
> by quasipatterns in E:
> <http://www.erights.org/elang/grammar/quasi-overview.html>
>
> (That page unfortunately assumes a lot of context that might be opaque
> to people not familiar with E, but hopefully the main ideas will come
> through.)
>
> Quasipatterns are more general because, as well as being able to make
> substitutions (what you call metacurrying), they also allow pattern
> matching on programs without having to know the abstract form. For
> example:
>
>   /**
>    * What's the derivative of expr with respect to var? I.e. what's
>    * "d(expr)/d(var)"?
>    */
>   def deriv(expr, var) :any {
>       switch (expr) {
>           # ** means "to the power"
>           match e`$var ** @exp` ? (isConst(exp)) {
>               e`$exp * $var ** ($exp - 1)`
>           }
>           match e`@a + @b` {
>               e`${deriv(a, var)} + ${deriv(b, var)}`
>           }
>           ...  # other differentiable expressions
>       }
>   }
>
> Also, quasipatterns are designed to be able to process multiple languages,
> and even mixtures of languages, while still being able to express simple
> cases simply.
>
> --
> David Hopwood <>
>
>
>
>



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