Clojure 1.7.0-alpha4 is now available.
Try it via
- Download:
http://central.maven.org/maven2/org/clojure/clojure/1.7.0-alpha4/
- Download securely:
https://repo1.maven.org/maven2/org/clojure/clojure/1.7.0-alpha4/
- Leiningen: [org.clojure/clojure "1.7.0-alpha4"]
A few important changes to be aware of:
1) CLJ-1330 (added in 1.7.0-alpha3) contained an enhancement to include
local names in class names. This introduced some problems due to class
name lengths. That aspect of CLJ-1330 has been retracted and this should
no longer be an issue.
2) CLJ-1578 highlighted an issue where new Clojure core functions
("update" in this case) could cause errors to be thrown on reload with
existing code bases that used that function name. This will now emit a
warning instead of throwing an exception. This should make it safer to
upgrade to new Clojure versions without incurring errors.
3) CLJ-1529 avoids unnecessary calls to Class.forName() and can
significantly reduce compile time on some (not all) projects.
For all changes new in alpha4, see the issues marked "(alpha4)" in the
full changes below.
------------------------------------------------------------
Clojure 1.7.0-alpha4 has the changes below from 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
* cycle
* take-nth
* replace
* partition-by
* partition-all
* keep
* keep-indexed
Additionally some new transducer functions have been added:
* cat - concatenates the contents of each input
* de-dupe - 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/seqable/iterable seq of applications of
the transducer to items in coll. Applications are re-performed with every
reduce/seq/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) (alpha4)
### 1.2 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.
### 1.3 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)
### 1.4 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)
## 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](http://dev.clojure.org/jira/browse/CLJ-1477)
Fix typo in deftype docstring
* [CLJ-1478](http://dev.clojure.org/jira/browse/CLJ-1378)
Fix typo in clojure.main usage
### 2.3 Performance
* [CLJ-1430](http://dev.clojure.org/jira/browse/CLJ-1430)
Improve performance of partial with more unrolling
* [CLJ-1384](http://dev.clojure.org/jira/browse/CLJ-1384)
clojure.core/set should use transients for better performance
* [CLJ-1429](http://dev.clojure.org/jira/browse/CLJ-1429)
Cache unknown multimethod value default dispatch
* [CLJ-1529](http://dev.clojure.org/jira/browse/CLJ-1529) (alpha4)
Reduce compile times by avoiding unnecessary calls to Class.forName()
### 2.4 Other enhancements
* [CLJ-1191](http://dev.clojure.org/jira/browse/CLJ-1191)
Improve apropos to show some indication of namespace of symbols found
* [CLJ-1378](http://dev.clojure.org/jira/browse/CLJ-1378)
Hints don't work with #() form of function
* [CLJ-1498](http://dev.clojure.org/jira/browse/CLJ-1498)
Removes owner-thread check from transients - this check was preventing
some valid usage of transients in core.async where a transient is created
on one thread and then used again in another pooled thread (while still
maintaining thread isolation).
* [CLJ-803](http://dev.clojure.org/jira/browse/CLJ-803)
Extracted IAtom interface implemented by Atom.
* [CLJ-1315](http://dev.clojure.org/jira/browse/CLJ-1315)
Don't initialize classes when importing them
* [CLJ-1330](http://dev.clojure.org/jira/browse/CLJ-1330) (alpha4)
Class name clash between top-level functions and defn'ed ones
* [CLJ-1349](http://dev.clojure.org/jira/browse/CLJ-1349) (alpha4)
Update to latest test.generative and add dependency on test.check
## 3 Bug Fixes
* [CLJ-1362](http://dev.clojure.org/jira/browse/CLJ-1362)
Reduce broken on some primitive vectors
* [CLJ-1388](http://dev.clojure.org/jira/browse/CLJ-1388)
Equality bug on records created with nested calls to map->record
* [CLJ-1274](http://dev.clojure.org/jira/browse/CLJ-1274)
Unable to set compiler options via system properties except for AOT
compilation
* [CLJ-1241](http://dev.clojure.org/jira/browse/CLJ-1241)
NPE when AOTing overrided clojure.core functions
* [CLJ-1185](http://dev.clojure.org/jira/browse/CLJ-1185)
reductions does not check for reduced value
* [CLJ-1039](http://dev.clojure.org/jira/browse/CLJ-1039)
Using def with metadata {:type :anything} throws ClassCastException
during printing
* [CLJ-887](http://dev.clojure.org/jira/browse/CLJ-887)
Error when calling primitive functions with destructuring in the arg
vector
* [CLJ-823](http://dev.clojure.org/jira/browse/CLJ-823)
Piping seque into seque can deadlock
* [CLJ-738](http://dev.clojure.org/jira/browse/CLJ-738)
<= is incorrect when args include Double/NaN
* [CLJ-1408](http://dev.clojure.org/jira/browse/CLJ-1408)
Make cached string value of Keyword and Symbol transient
* [CLJ-1466](http://dev.clojure.org/jira/browse/CLJ-1466)
clojure.core/bean should implement Iterable
* [CLJ-1578](http://dev.clojure.org/jira/browse/CLJ-1578) (alpha4)
Make refer of Clojure core function not throw exception on reload
* [CLJ-1501](http://dev.clojure.org/jira/browse/CLJ-1501) (alpha4)
LazySeq equals() should not use equiv() logic
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