Clojure #= reader macro

Question

I just "discovered" the #= reader macro from a post on Stackoverflow and it solves a problem. How likely is this reader macro to become an official (documented) part of the language? How about deprecated or changed behavior?

The #= reader macro causes the following s-expression to be evaluated by the Lisp reader (before macro expansion).

Jouni K. Seppänen · Accepted Answer · 2011-06-21 20:27:25Z

5

It is used by the core language when something is printed with *print-dup* true, so I'd wager that it is going to stay. No idea why it is not documented.

user=> (binding [*print-dup* true] (prn {:foo 1 :bar 2}))
#=(clojure.lang.PersistentArrayMap/create {:foo 1, :bar 2})
nil

answered Jun 21, 2011 at 20:27

Jouni K. Seppänen

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1 Comment

Ralph Over a year ago

Thanks. I also wonder why it's not documented. It would be useful in macros to evaluate a sub-expression before the macro expands.

solussd · Accepted Answer · 2012-02-03 14:05:39Z

3

It's not documented because it could go away / be replaced with something else. I wouldn't recommend using it in your programs.

answered Feb 3, 2012 at 14:05

solussd

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