Well, I must say I'm even more ignorant in how the feature expansions are 
implemented. Is the feature a thing that each implementation defines 
separately? If so, then it will be easy to set our fork's feature as :clja, 
or whatever else. My request to you would then be: can you please include 
:clja into the "spec", in the list of available features? What I ask for is 
sort of semi-official confirmation that Clojure-Android has its own 
feature, so that we would have easier time to include Android-specific code 
into the libraries that will become cross-platform after 1.7 goes live.

Best regards,
Alex

On Monday, April 6, 2015 at 12:34:04 AM UTC+3, Alex Miller wrote:
>
> The reader can be invoked programmatically with any feature set you like 
> now. We did not plan to allow custom features for 1.7.
>
> I'm not sure what it would mean to "add" an android feature? I'll plead 
> ignorance in not knowing how the Clojure 
> Android stuff works or where a feature indicating Android could be set 
> without support for custom features. Do you currently fork to support 
> Android?
>
>
>
> On Apr 5, 2015, at 1:44 PM, Alexander Yakushev <al...@bytopia.org 
> <javascript:>> wrote:
>
> Hello Alex,
>
> As I've understood from the dev.clojure.org page, additional features and 
> feature combinations will become available later. Can we please get 
> :clj/android (or :clja) still in 1.7? If so, what has to be done by me or 
> Daniel to make it happen?
>
> Thanks!
>
> On Tuesday, March 31, 2015 at 7:50:27 PM UTC+3, Alex Miller wrote:
>
> Clojure 1.7.0-alpha6 is now available.
>
> Try it via
> - Download: 
> https://repo1.maven.org/maven2/org/clojure/clojure/1.7.0-alpha6/
> - Leiningen: [org.clojure/clojure "1.7.0-alpha6"]
>
> Regression fixes from previous alphas (and one from 1.6):
>
> 1) CLJ-1544 was rolled back and will be investigated for a future release.
> 2) CLJ-1637 fixed regression with vec on MapEntry 
> 3) CLJ-1663 fixed regression in classloader (affected Cursive)
> 4) CLJ-1638 fixed regression with removed PersistentVector.create(List) 
> method
> 5) CLJ-1681 fixed regression in 1.6 with NPE on reflection warning for 
> literal nil arg
> 6) CLJ-1604 fixed problem with AOT and shadowing clojure.core symbols that 
> prevented update
>
> Some highlights new in alpha6:
>
> ## Transducer-related changes:
>
> The LazyTransformer introduced to create lazy transforming sequences has 
> been 
> replaced with a TransformingIterator. This was done to simplify the code
> around transformations and to make certain use cases around eduction more 
> efficient.
>
> ## Faster reduce, iterator, and sequence paths
>
> A lot of work has been done across a set of tickets to improve the ability 
> of
> collections to provide more efficient reduce or iterator performance, and 
> also to
> make common sequence generators create faster sequence and reduce paths. 
> You
> should see significant performance in many reduce-related paths (this 
> includes 
> reduce, transduce, into, and anything else built on reduce). 
>
> Many of those changes also have beneficial sequence performance, so you 
> may see
> some benefits even in code that does not use transducers.
>
> * Most uses of SeqIterator have now been replaced with iterators that 
> directly walk
> the underlying source for improved efficiency. This includes maps, sets, 
> records, etc.
> * repeat - now returns a faster sequence with a fast reduce path
> * cycle - now returns a faster sequence with a fast reduce path
> * iterate - now returns a faster sequence with a fast reduce path
> * range - (did not quite make it in, but coming soon...)
> * keys - iterates directly over the keys of a map, without seq or MapEntry 
> allocation
> * vals - iterates directly over the vals of a map, without seq or MapEntry 
> allocation
> * iterator-seq - now creates a chunked sequence when previously it was 
> unchunked
> * vec and set - were not changed in this release but were set up in a 
> previous alpha
>   to take advantage of the reduce and iterator changes above
>
> ## Reader conditionals
>
> Reader Conditionals is a new capability to support portable code that
> can run on multiple Clojure platforms with only small changes. In
> particular, this feature aims to support the increasingly common case
> of libraries targeting both Clojure and ClojureScript.
>
> Code intended to be common across multiple platforms should use a new
> supported file extension: ".cljc". When requested to load a namespace,
> the platform-specific file extension (.clj, .cljs) will be checked
> prior to .cljc.
>
> A new reader form can be used to specify "reader conditional" code in
> cljc files (and *only* cljc files). Each platform defines a feature
> identifying the platform (:clj, :cljs, :cljr). The reader conditional
> specifies code that is read conditionally based on the feature/
>
> Form #? takes a list of alternating feature and expression. These are
> checked like cond and the selected expression is read and returned. Other
> branches are unread. If no branch is selected, the reader reads nothing
> (not nil, but literally as if reading ""). An optional ":default" branch
> can be used as a fallthrough.
>
> Reader conditional with 2 features and a default:
>
> #?(:clj     Double/NaN
>    :cljs    js/NaN
>    :default nil)
>
> There is also a reader conditional splicing form. The evaluated expression
> should be sequential and will be spliced into the surrounded code, similar
> to unqoute-splicing.
>
> For example:
>
>    [1 2 #?@(:clj [3 4] :cljs [5 6])]
>
> This form would read as [1 2 3 4] on Clojure, [1 2 5 6] on ClojureScript,
> and [1 2] on any other platform.
>
> Additionally, the reader can now be invoked with options for the features
> to use and how to interpret reader conditionals. By default, reader 
> conditionals
> are not allowed, but that can be turned on, or a "preserve" mode can be 
> used to
> preserve all branches (most likely useful for tooling or source 
> transforms).
>
> In the preserve mode, the reader conditional itself and any tagged literals
> within the unselected branches are returned as tagged literal data.
>
> For more information, see:
> http://dev.clojure.org/display/design/Reader+Conditionals
>
> Two important side notes:
> - Clojure dependencies have been updated and you must re-run antsetup.sh 
> if you
> build Clojure locally with ant.
> - The equivalent ClojureScript support for reader conditionals is not yet 
> available
> but is a top priority to release as soon as possible... stay tuned.
>
> ## Printing as data
>
> There have been enhancements in how the REPL prints values without a
> print-method, specifically Throwable and the fallthrough Object case.
> Both cases now print in a tagged literal data form that can be read
> by the reader.
>
> Unhandled objects print with the class, hash code, and toString:
>
> user=> *ns*
> #object[clojure.lang.Namespace 0x55aa628 "user"]
>
> Thrown exceptions will still be printed in the normal way by the default
> REPL but printing them to a stream will show a different form:
>
> user=> (/ 1 0)
> ArithmeticException Divide by zero  clojure.lang.Numbers.divide 
> (Numbers.java:158)
> user=> (println *e)
> #error{:cause Divide by zero,
>    :via [{:type java.lang.ArithmeticException,
>       :message Divide by zero,
>   :at [clojure.lang.Numbers divide Numbers.java 158]}],
>    :trace
>      [[clojure.lang.Numbers divide Numbers.java 158]
>   [clojure.lang.Numbers divide Numbers.java 3808]
>   [user$eval5 invoke NO_SOURCE_FILE 3]
>   ;; elided ...
>   ]]}
>   
> For all changes new in alpha6, see the issues marked "(alpha6)" in the
> full changes below.
>
> ------------------------------------------------------------
> Clojure 1.7.0-alpha6 has the following updates since 1.6.0:
>
> ## 1 New and Improved Features
>
> ### 1.1 Transducers
>
> Transducers is a new way to decouple algorithmic transformations from their
> application in different contexts. Transducers are functions that transform
> reducing functions to build up a "recipe" for transformation.
>
> Also see: http://clojure.org/transducers
>
> Many existing sequence functions now have a new arity (one fewer argument
> than before). This arity will return a transducer that represents the same
> logic but is independent of lazy sequence processing. Functions included 
> are:
>
> * conj (conjs to [])
> * map
> * mapcat
> * filter
> * remove
> * take
> * take-while
> * drop
> * drop-while
> * take-nth
> * replace
> * partition-by
> * partition-all
> * keep
> * keep-indexed
> * map-indexed
> * distinct
> * interpose
>
> Additionally some new transducer functions have been added:
>
> * cat - concatenates the contents of each input
> * dedupe - removes consecutive duplicated values
> * random-sample - returns items from coll with random probability
>
> And this function can be used to make completing transforms:
>
> * completing
>
> There are also several new or modified functions that can be used to apply
> transducers in different ways:
>
> * sequence - takes a transformation and a coll and produces a lazy seq
> * transduce - reduce with a transformation (eager)
> * eduction - returns a reducible/iterable of applications of the 
> transducer to items in coll. Applications are re-performed with every 
> reduce/iterator.
> * run! - run the transformation for side effects on the collection
>
> There have been a number of internal changes to support transducers:
>
> * volatiles - there are a new set of functions (volatile!, vswap!, 
> vreset!, volatile?) to create and use volatile "boxes" to hold state in 
> stateful transducers. Volatiles are faster than atoms but give up atomicity 
> guarantees so should only be used with thread isolation.
> * array iterators - added support for iterators over arrays
>
> Some related issues addressed during development:
> * [CLJ-1511](http://dev.clojure.org/jira/browse/CLJ-1511)
> * [CLJ-1497](http://dev.clojure.org/jira/browse/CLJ-1497)
> * [CLJ-1549](http://dev.clojure.org/jira/browse/CLJ-1549)
> * [CLJ-1537](http://dev.clojure.org/jira/browse/CLJ-1537)
> * [CLJ-1554](http://dev.clojure.org/jira/browse/CLJ-1554)
> * [CLJ-1601](http://dev.clojure.org/jira/browse/CLJ-1601)
> * [CLJ-1606](http://dev.clojure.org/jira/browse/CLJ-1606)
> * [CLJ-1621](http://dev.clojure.org/jira/browse/CLJ-1621)
> * [CLJ-1600](http://dev.clojure.org/jira/browse/CLJ-1600)
> * [CLJ-1635](http://dev.clojure.org/jira/browse/CLJ-1635) (alpha6)
> * [CLJ-1683](http://dev.clojure.org/jira/browse/CLJ-1683) (alpha6)
> * [CLJ-1669](http://dev.clojure.org/jira/browse/CLJ-1669) (alpha6)
>
> ### 1.2 Reader Conditionals (alpha6)
>
> Reader Conditionals is a new capability to support portable code that
> can run on multiple Clojure platforms with only small changes. In
> particular, this feature aims to support the increasingly common case
> of libraries targeting both Clojure and ClojureScript.
>
> Code intended to be common across multiple platforms should use a new
> supported file extension: ".cljc". When requested to load a namespace,
> the platform-specific file extension (.clj, .cljs) will be checked
> prior to .cljc.
>
> A new reader form can be used to specify "reader conditional" code in
> cljc files (and *only* cljc files). Each platform defines a feature
> identifying the platform (:clj, :cljs, :cljr). The reader conditional
> specifies code that is read conditionally based on the feature/
>
> Form #? takes a list of alternating feature and expression. These are
> checked like cond and the selected expression is read and returned. Other
> branches are unread. If no branch is selected, the reader reads nothing
> (not nil, but literally as if reading ""). An optional ":default" branch
> can be used as a fallthrough.
>
> Reader conditional with 2 features and a default:
>
> #?(:clj     Double/NaN
>    :cljs    js/NaN
>    :default nil)
>
> There is also a reader conditional splicing form. The evaluated expression
> should be sequential and will be spliced into the surrounded code, similar
> to unqoute-splicing.
>
> For example:
>
>    [1 2 #?@(:clj [3 4] :cljs [5 6])]
>
> This form would read as [1 2 3 4] on Clojure, [1 2 5 6] on ClojureScript,
> and [1 2] on any other platform.
>
> Additionally, the reader can now be invoked with options for the features
> to use and how to interpret reader conditionals. By default, reader 
> conditionals
> are not allowed, but that can be turned on, or a "preserve" mode can be 
> used to
> preserve all branches (most likely useful for tooling or source 
> transforms).
>
> In the preserve mode, the reader conditional itself and any tagged literals
> within the unselected branches are returned as tagged literal data.
>
> For more information, see:
> http://dev.clojure.org/display/design/Reader+Conditionals
>
> * [CLJ-1424](http://dev.clojure.org/jira/browse/CLJ-1424)
>
> ### 1.3 Keyword and Symbol Construction
>
> In response to issues raised in [CLJ-1439](
> http://dev.clojure.org/jira/browse/CLJ-1439),
> several changes have been made in symbol and keyword construction:
>
> 1) The main bottleneck in construction of symbols (which also occurs 
> inside keywords) was
> interning of the name and namespace strings. This interning has been 
> removed, resulting
> in a performance increase.
>
> 2) Keywords are cached and keyword construction includes a cache check. A 
> change was made
> to only clear the cache reference queue when there is a cache miss.
>
> ### 1.4 Warn on Boxed Math
>
> One source of performance issues is the (unintended) use of arithmetic 
> operations on
> boxed numbers. To make detecting the presence of boxed math easier, a 
> warning will now
> be emitted about boxed math if \*unchecked-math* is set to :warn-on-boxed 
> (any truthy
> value will enable unchecked-math, only this specific value enables the 
> warning).
>
> Example use:
>
>     user> (defn plus-2 [x] (+ x 2))  ;; no warning, but boxed
> #'user/plus-2
>     user> (set! *unchecked-math* :warn-on-boxed)
> true
>     user> (defn plus-2 [x] (+ x 2)) ;; now we see a warning
>     Boxed math warning, NO_SOURCE_PATH:10:18 - call: public static 
> java.lang.Number
> clojure.lang.Numbers.unchecked_add(java.lang.Object,long).
>     #'user/plus-2
> user> (defn plus-2 [^long x] (+ x 2)) ;; use a hint to avoid boxing
> #'user/plus-2
>
> * [CLJ-1325](http://dev.clojure.org/jira/browse/CLJ-1325)
> * [CLJ-1535](http://dev.clojure.org/jira/browse/CLJ-1535)
> * [CLJ-1642](http://dev.clojure.org/jira/browse/CLJ-1642) (alpha6)
>
> ### 1.5 update - like update-in for first level
>
> `update` is a new function that is like update-in specifically for 
> first-level keys:
>
>     (update m k f args...)
>
> Example use:
>
>     user> (update {:a 1} :a inc)
> {:a 2}
> user> (update {:a 1} :a + 2)
> {:a 3}
> user> (update {} :a identity)  ;; missing returns nil
> {:a nil}
>
> * [CLJ-1251](http://dev.clojure.org/jira/browse/CLJ-1251)
>
> ### 1.6 Faster reduce and iterator paths (alpha6)
>
> Several important Clojure functions now return sequences that also
> contain fast reduce() (or in some cases iterator()) paths. In many
> cases, the new implementations are also faster for lazy sequences
>
> * repeat - now implements IReduce
> * cycle - implements IReduceInit
> * iterate - implements IReduceInit
> * range - implements IReduce, specialized case handles common case of all 
> longs
> * keys - iterates directly over the keys of a map, without seq or MapEntry 
> allocation
> * vals - iterates directly over the vals of a map, without seq or MapEntry 
> allocation
> * iterator-seq - creates a chunked sequence when previously it was 
> unchunked
>
> Additionally, hash-maps and hash-sets now provide iterators that walk
> the data structure directly rather than via a sequence.
>
> A new interface (IMapIterable) for direct key and val iterators on maps
> was added. External data structures can use this interface to provide
> direct key and val iterators via keys and vals.
>
> These enhancements are particularly effective when used
> in tandem with transducers via transduce, sequence, into, and
> eduction.
>
> * [CLJ-1603](http://dev.clojure.org/jira/browse/CLJ-1603)
> * [CLJ-1515](http://dev.clojure.org/jira/browse/CLJ-1515)
> * [CLJ-1602](http://dev.clojure.org/jira/browse/CLJ-1602)
> * [CLJ-1669](http://dev.clojure.org/jira/browse/CLJ-1669)
>
> ### 1.7 Printing as data (alpha6)
>
> There have been enhancements in how the REPL prints values without a
> print-method, specifically Throwable and the fallthrough Object case.
> Both cases now print in a tagged literal data form that can be read
> by the reader.
>
> Unhandled objects print with the class, hash code, and toString:
>
> user=> *ns*
> #object[clojure.lang.Namespace 0x55aa628 "user"]
>
> Thrown exceptions will still be printed in the normal way by the default
> REPL but printing them to a stream will show a different form:
>
> user=> (/ 1 0)
> ArithmeticException Divide by zero  clojure.lang.Numbers.divide 
> (Numbers.java:158)
> user=> (println *e)
> #error{:cause Divide by zero,
>    :via [{:type java.lang.ArithmeticException,
>       :message Divide by zero,
>   :at [clojure.lang.Numbers divide Numbers.java 158]}],
>    :trace
>      [[clojure.lang.Numbers divide Numbers.java 158]
>   [clojure.lang.Numbers divide Numbers.java 3808]
>   [user$eval5 invoke NO_SOURCE_FILE 3]
>   ;; elided ...
>   ]]}
>
> ## 2 Enhancements
>
> ### 2.1 Error messages
>
> * [CLJ-1261](http://dev.clojure.org/jira/browse/CLJ-1261)
>   Invalid defrecord results in exception attributed to consuming ns 
> instead of defrecord ns
> * [CLJ-1169](http://dev.clojure.org/jira/browse/CLJ-1169)
>   Report line,column, and source in defmacro errors
> * [CLJ-1297](http://dev.clojure.org/jira/browse/CLJ-1297)
>   Give more specific hint if namespace with "-" not found to check file 
> uses "_"
>
> ### 2.2 Documentation strings
>
> * [CLJ-1417](http://dev.clojure.org/jira/browse/CLJ-1417)
>   clojure.java.io/input-stream has incorrect docstring
> * [CLJ-1357](http://dev.clojure.org/jira/browse/CLJ-1357)
>   Fix typo in gen-class doc-string
> * [CLJ-1479](http://dev.clojure.org/jira/browse/CLJ-1479)
>   Fix typo in filterv example
> * [CLJ-1480](http://dev.clojure.org/jira/browse/CLJ-1480)
>   Fix typo in defmulti docstring
> * [CLJ-1477](
>
> ...

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