Re: using regex reader macro with generated code

[Daniel Werner]

On Jun 16, 4:47 am, Alex Baranosky <alexander.barano...@gmail.com>
wrote:
> IS it possible to use the regex reader macro #"" with generated code?  What
> I mean is do something like:
>
> #"${(join "|" (range 1 10000))}"
>
> I'm using ${...} to mean string interpolation, though I know Clojure doesn't
> have that syntax.  Is there a way to get this effect or must I use
> (re-pattern (join "|" (range 1 10000)))

In your specific example, as all the components used to build your
regex are static, you could use re-pattern as a macro:

(defmacro re-ra­nge []
  (re-p­attern (cloj­ure.string­/join "|" (rang­e 1 1000)­)

However, as soon as you want to parameterise the regex, things get
hairy. You *could* have your macro take arguments like this:

; bad idea
(defmacro re-ra­nge [start end]
  (re-p­attern (cloj­ure.string­/join "|" (rang­e start end­)

This would work as long as the macro is passed static values, like 1
and 1000. This, however, *won't* work:

(let [x 1000]
  (re-range 1 x)

In this case #'re-range macro would receive the symbol 'x as its end
argument, because macros are executed at compile time (or macro
expansion time, to be more precise) and take code as their data.

Hope that helps,
--
Daniel

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