> On Wed, Mar 12, 2008 at 9:35 PM, Rich Hickey <richhic...@gmail.com> wrote:

> [...]

> >  As time goes by I become more entrenched in my decision not to
> >  support reader macros. While reader macros afford a lot
> >  of power, they come at a price in lack of interoperability, much more
> >  so than ordinary macros, which can be placed in namespaces.

> I believe Clojure can provide reader macros that do not affect
> interoperability at all. Reader macros cause problems when a
> read-table modification performed in one source file affects other
> source files that did not expect such a modification. I'd suggest
> preventing such read-table damage as follows:
> ...
> Other potential issues:

> * Two different libraries may use the same dispatch characters by
> default,

> but this can be solved easily if the libraries allow the
> client code to specify the dispatch characters they should attach
> their reader macros to. For instance:

> (enable-interpolate-syntax \I) ; Uses #I"" for interpolating strings.

> If the libraries do not allow choosing the dispatch character, they
> cannot be used together in the same source file, but that can be
> easily fixed (presuming you have the source, or don't mind
> re-modifying the read-table after the library has done its thing), and
> that little inconvenience is preferable to not having any reader macro
> support. :-)

> As you note, reader macros provide a lot of power, and while most code
> will never need reader macros, some code can benefit powerfully from
> them. It is possible to fake reader macros in very roundabout ways
> (provide custom definitions of load and read that check characters
> against a dispatch table, and call the underlying read for characters
> not in the custom dispatch table), but life would be a lot easier if
> the language supports them directly.

> What do you think of this proposal? If there's no interest in (safe)
> reader macros at all, I'll drop this discussion, but if there is
> interest, I'd be delighted to put together a prototype.