[plt-scheme] Very basic macro question

From: johny seventy (johnyseventy at hotmail.com)
Date: Tue Jan 19 13:26:31 EST 2010

> Date: Sun, 17 Jan 2010 18:42:32 +0000
> Subject: Re: [plt-scheme] Very basic macro question
> From: noelwelsh at gmail.com
> To: johnyseventy at hotmail.com
> CC: plt-scheme at list.cs.brown.edu
> On Sun, Jan 17, 2010 at 2:22 PM, johny seventy <johnyseventy at hotmail.com> wrote:
> > I understand why example
> > four works but is there anyway I can do this without eval?
> A transformer binding and syntax-local-value.
> It doesn't make sense to parameterise a macro by a run-time value --
> macros are expanded before run-time so they cannot depend on run-time
> values.
> N.

Thanks for the responses. I just want to clarify one more thing.

I have an sexpr which is created dynamically at runtime and I want to transform this sexpr. It seemed really easy to do the transformation using a syntax-rules macro. So the problem is I have missed the boat at this stage as macro expansion has already taken place. The only way I can see how to invoke the macro at this stage is by using eval. I am not sure what you mean by a transformer binding and syntax-local-value. Is there a simple example of this in action I could take a look at?

Thanks for your patience. 

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