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**Subject**: **Re: Adding several methamethods could be helpful**
**From**: steve donovan <steve.j.donovan@...>
**Date**: Sun, 27 Mar 2011 15:28:32 +0200

On Sun, Mar 27, 2011 at 2:34 PM, Francesco Abbate
<francesco.bbt@gmail.com> wrote:
> new matrix. I don't have a solution for the problem but I was thinking
> that a sort of lazy evaluation could work. Here is the idea. When you
> type an expression like A+B the object that is created is a new type
> of object that just store the information that a sum of A and B should
> be done.
Something like that is done with with Penlight's placeholder
expressions[1]. The problem here is that you want to 'quote' an
expression and not evaluate it immediately, and later compile this
into a function.[2] But once you have your expression in this form,
you can do symbolic operations like differentiation [3]
So something like a + b*t can be represented in a AST form, and then
compiled into optimal code for the particular types.
steve d.
[1] http://stevedonovan.github.com/Penlight/#T36
[2] a runtime equivalent of that crazy C++ template expression stuff
than Fabien was alluding to.
[3] https://github.com/stevedonovan/Penlight/blob/master/examples/symbols.lua