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changelog updates for 1.7.0-alpha6
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Signed-off-by: Stuart Halloway <stu@cognitect.com>
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puredanger authored and stuarthalloway committed Mar 27, 2015
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Expand Up @@ -51,7 +51,7 @@ 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.
* 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:
Expand All @@ -69,8 +69,64 @@ Some related issues addressed during development:
* [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)
* [CLJ-1683](http://dev.clojure.org/jira/browse/CLJ-1683)
* [CLJ-1669](http://dev.clojure.org/jira/browse/CLJ-1669)

### 1.2 Keyword and Symbol Construction
### 1.2 Reader Conditionals

Reader Conditionals is a new capability to support portable code that

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@arrdem

arrdem Mar 27, 2015

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s/is/are/g
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.

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@Bronsa

Bronsa Apr 10, 2015

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typo (unqoute)

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:
Expand All @@ -82,7 +138,7 @@ 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
### 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
Expand All @@ -104,8 +160,9 @@ Example use:

* [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)

### 1.4 update - like update-in for first level
### 1.5 update - like update-in for first level

`update` is a new function that is like update-in specifically for first-level keys:

Expand All @@ -122,6 +179,65 @@ Example use:

* [CLJ-1251](http://dev.clojure.org/jira/browse/CLJ-1251)

### 1.6 Faster reduce and iterator paths

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

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
Expand Down Expand Up @@ -185,6 +301,14 @@ Example use:
set now works with things that only implement Iterable or IReduceInit
* [CLJ-1633](http://dev.clojure.org/jira/browse/CLJ-1633)
PersistentList/creator doesn't handle ArraySeqs correctly
* [CLJ-1589](http://dev.clojure.org/jira/browse/CLJ-1589)
Clean up unused paths in InternalReduce
* [CLJ-1677](http://dev.clojure.org/jira/browse/CLJ-1677)
Add setLineNumber() to LineNumberingPushbackReader
* [CLJ-1667](http://dev.clojure.org/jira/browse/CLJ-1667)
Change test to avoid using hard-coded socket port
* [CLJ-1683](http://dev.clojure.org/jira/browse/CLJ-1683)
Change reduce tests to better catch reduce without init bugs

## 3 Bug Fixes

Expand Down Expand Up @@ -224,8 +348,23 @@ Example use:
Some IReduce/IReduceInit implementors don't respect reduced
* [CLJ-979](http://dev.clojure.org/jira/browse/CLJ-979)
Clojure resolves to wrong deftype classes when AOT compiling or reloading
* [CLJ-1544](http://dev.clojure.org/jira/browse/CLJ-1544)
AOT bug involving namespaces loaded before AOT compilation started
* [CLJ-1636](http://dev.clojure.org/jira/browse/CLJ-1636)
Fix intermittent SeqIterator problem by removing use of this as a sentinel
* [CLJ-1637](http://dev.clojure.org/jira/browse/CLJ-1636)
Fix regression from CLJ-1546 that broke vec on MapEntry
* [CLJ-1663](http://dev.clojure.org/jira/browse/CLJ-1663)
Fix regression from CLJ-979 for DynamicClassLoader classloader delegation
* [CLJ-1604](http://dev.clojure.org/jira/browse/CLJ-1604)
Fix error from AOT'ed code defining a var with a clojure.core symbol name
* [CLJ-1561](http://dev.clojure.org/jira/browse/CLJ-1561)
Fix incorrect line number reporting for error locations
* [CLJ-1568](http://dev.clojure.org/jira/browse/CLJ-1568)
Fix incorrect line number reporting for error locations
* [CLJ-1638](http://dev.clojure.org/jira/browse/CLJ-1638)
Fix regression from CLJ-1546 removed PersistentVector.create(List) method
* [CLJ-1681](http://dev.clojure.org/jira/browse/CLJ-1681)
Fix regression from CLJ-1248 (1.6) in reflection warning with literal nil argument


# Changes to Clojure in Version 1.6

Expand Down

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