Please Vote: Exercises in TDPL?

[Bill Baxter]

On Fri, May 15, 2009 at 7:40 PM, Georg Wrede <georg.wrede at iki.fi> wrote:
> Bill Baxter wrote:
>>
> Incidentally, here, or in D.learn, somebody was asking for symbolic
> derivation with D templates. I think one of the excercises in SICP was to
> write a lisp snippet that did just that.

You're probably thinking of my message about automatic
differentiation.  Automatic differentiation is not the same as
symbolic differentiation.   Symbolic differentiation is not really
very useful in practice since expressions tend to balloon out into
huge messes.   It also only works on things that are differentiable
functions.   Automatic differentiation, on the other hand, works on
code rather than on mathematical functions.   You can run AD on loops
and other things that symbolic differentiation just doesn't know how
to handle, and all of this can be done in O(N) where N is the
complexity of the forward expression.  I posted a bunch of links in
that other thread that explain the difference in more detail if you'd
like to know more.

--bb