[clean-list] Is it possible to use Dynamics to do Multi-Stage Programming in Clean?

[Arjen van Weelden]

Hi Alexsandro,

It's not clear to me why you keep wrapping dynamics in dynamics. You can
use pattern matching (on the value and the type) to extract the
expression. For instance:

Start :: Int
Start = c     // the answer would be 9
  where
    a = dynamic 1 + 2
    b = case a of (x :: Int) -> dynamic x * x
    c = execute b

execute :: Dynamic -> a | TC a
execute (x :: a) = x

I found the following definition: "Multi-stage programming (MSP) is a
paradigm for developing generic software that does not pay a runtime
penalty ...". I'm afraid that my answer has nothing to do with
'Multi-Stage Programming'. Using dynamics, you will always have a
run-time penalty. I looks like you need something like Template Haskell
or MetaOCaml.

kind regards,
	Arjen

Alexsandro Soares wrote:
> Hi all,
> 
>   I'm tryng to make a strongly-typed genetic
> programming system in Clean. I'm thinking in use the
> Dynamics feature to simulate multi-stage programming,
> but I'm not sure about this... 
>   What's wrong with the following code? How can I
> implement the "execute" function?
> 
> -------- Test.icl --------------------------
> module Test
> 
> import StdEnv
> import StdDynamic
> import StdDynamicFileIO
> 
> Start = c     // the answer would be 9
>   where
>     a = dynamic (1+2) // dynamically generates source
> code at runtime and delay its execution
>     b = dynamic (a * a) // combine the delayed values
> to construct larger ones
>     c = execute b       // compile and execute the
> dynamically generated code
> 
> ------------------------------
> 
>   Thanks in advance for any answer.
> 
>    Cheers,
>    Alex