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[CLJS-27] Conditional compilation (or reading) Created: 22/Jul/11  Updated: 06/Aug/14

Status: Open
Project: ClojureScript
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Rich Hickey Assignee: Unassigned
Resolution: Unresolved Votes: 10
Labels: None

Attachments: File cljs-27.diff     File conditional-compilation-clojure.diff     File conditional-compilation-clojurescript.diff    
Patch: Code and Test
Approval: Vetted


As people start trying to write libs that are portable between Clojure and ClojureScript they might need to have a bit of branching on target. N.B. supporting this means a change to Clojure, although it has general utility there as well.

Consider CL #+ #- reader macros - http://www.lispworks.com/documentation/lw50/CLHS/Body/02_dhq.htm

Patch: cljs-27.diff

Related: CLJ-1424, TRDR-14

Comment by Roman Scherer [ 19/Jul/12 8:52 AM ]

The following patches include an implementation of Common Lisp's #+
and #- reader macros to allow conditional compilation/reading for
Clojure and ClojureScript.

The patches add a dynamic variable called features to the
clojure.core and cljs.core namespaces, that should contain the
supported features of the platform in question as keywords.

Unlike in Common Lisp, the variable is a Clojure set and not a list.
In Clojure the set contains at the moment the :clojure keyword, and in
ClojureScript the :clojurescript keyword.

I would like to get feedback on the names that are added to this
variable. Are those ok? Is :jvm for Clojure and :js for ClojureScript
better? Should ClojureScript add something like :rhino, :v8 or
:browser as well?

To run the ClojureScript tests, drop a JAR named "clojure.jar" that
has the Clojure patch applied into ClojureScript's lib directory.

Comment by David Nolen [ 19/Jul/12 12:18 PM ]

This is an enhancement so it probably requires a design page and extended discussion before it will go anywhere. Until that happens I'm marking this is as low priority.

Comment by Roman Scherer [ 19/Jul/12 1:45 PM ]

Ok. If someone could give me write access to the Clojure Dev Wiki I would be happy to start such a design page.

Comment by David Nolen [ 19/Jul/12 5:50 PM ]

If you've sent in your CA request permissions on the clojure-dev mailing list.

Comment by Roman Scherer [ 21/Jul/12 5:45 AM ]

I started a design page for this ticket in the Clojure Dev wiki:

Comment by Stuart Halloway [ 27/Jul/12 1:48 PM ]

Posting my comments over on the design page...

Comment by Alex Miller [ 06/Aug/14 7:42 AM ]

Latest patch updates into current ClojureScript and use of tools.reader/tools.analyzer etc. The reader changes are all in the accompanying tools.reader patch in TRDR-14. This patch adds support to allow a new option "features" which is expected to be a set of keywords. build will inject :cljs into this set. The feature set is maintained in clojure.tools.reader/*features*. set! is enhanced to special-case an update to *features* in the code (presumably a rarely-used feature).

Because tools.reader needs the supporting patch, I left in several changes that pull in a new version of tools.reader - I don't actually expect those to be the correct versions but they are there as a reminder to update all of the proper places.

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