1 Deprecated and Removed Features
1.1 Clojure 1.5 reducers library requires Java 6 or later
2 New and Improved Features
2.1 Reducers
2.2 Reader Literals improved
2.3 clojure.core/set-agent-send-executor!, set-agent-send-off-executor!, and send-via
2.4 New threading macros
2.5 Column metadata captured by reader
2.6 gen-class improvements
2.7 Support added for marker protocols
2.8 clojure.pprint/print-table output compatible with Emacs Org mode
2.9 clojure.string/replace and replace-first handle special characters more predictably
2.10 Set and map constructor functions allow duplicates
2.11 More functions preserve metadata
3 Performance Enhancements
4 Improved error messages
5 Improved documentation strings
6 Bug Fixes
The new reducers library (see below) requires Java 6 plus a ForkJoin library, or Java 7 or later. Clojure 1.5 can still be compiled and run with Java 5. The only limitations with Java 5 are that the new reducers library will not work, and building Clojure requires skipping the test suite (e.g. by using the command "ant jar").
Reducers provide a set of high performance functions for working with collections. The actual fold/reduce algorithms are specified via the collection being reduced. This allows each collection to define the most efficient way to reduce its contents.
The implementation details of reducers are available at the Clojure blog and therefore won't be repeated in these change notes. However, as a summary:
- There is a new namespace: clojure.core.reducers
- It contains new versions of map, filter etc based upon transforming reducing functions - reducers
- It contains a new function, fold, which is a parallel reduce+combine fold uses fork/join when working with (the existing!) Clojure vectors and maps
- Your new parallel code has exactly the same shape as your existing seq-based code
- The reducers are composable
- Reducer implementations are primarily functional - no iterators
- The model uses regular data structures, not 'parallel collections' or other OO malarkey
- It's fast, and can become faster still
- This is work-in-progress
Examples:
user=> (require '[clojure.core.reducers :as r])
user=> (reduce + (r/filter even? (r/map inc [1 1 1 2])))
;=> 6
;;red is a reducer awaiting a collection
user=> (def red (comp (r/filter even?) (r/map inc)))
user=> (reduce + (red [1 1 1 2]))
;=> 6
user=> (into #{} (r/filter even? (r/map inc [1 1 1 2])))
;=> #{2}
-
CLJ-1034 "Conflicting data-reader mapping" should no longer be thrown where there really isn't a conflict. Until this patch, having data_readers.clj on the classpath twice would cause the above exception.
-
CLJ-927 Added
*default-data-reader-fn*to clojure.core. When no data reader is found for a tag and*default-data-reader-fn*is non-nil, it will be called with two arguments, the tag and the value. If*default-data-reader-fn*is nil (the default), an exception will be thrown for the unknown tag.
Added two new functions:
-
clojure.core/set-agent-send-executor!
Allows the user to set the
java.util.concurrent.Executorused when callingclojure.core/send. Defaults to a fixed thread pool of size: (numCores + 2) -
clojure.core/set-agent-send-off-executor!
Allows the user to set the
java.util.concurrent.Executorused when callingclojure.core/send-off. Defaults to a cached thread pool. -
clojure.core/send-via
Like
send, andsend-off, except the first argument to this function is an executor to use when sending.
-
clojure.core/cond-> [expr & clauses]
Takes an expression and a set of test/form pairs. Threads the expression (via ->) through each form for which the corresponding test expression (not threaded) is true.
Example:
user=> (cond-> 1
true inc
false (* 42)
(= 2 2) (* 3))
6
-
clojure.core/cond->> [expr & clauses]
Takes an expression and a set of test/form pairs. Threads expr (via ->>) through each form for which the corresponding test expression (not threaded) is true.
Example:
user=> (def d [0 1 2 3])
#'user/d
user=> (cond->> d
true (map inc)
(seq? d) (map dec)
(= (count d) 4) (reduce +)) ;; no threading in the test expr
;; so d must be passed in explicitly
10
- clojure.core/as-> [expr name & forms]
Binds name to expr, evaluates the first form in the lexical context of that binding, then binds name to that result, repeating for each successive form
Note: this form does not actually perform any threading. Instead it allows the user to assign a name and lexical context to a value created by a parent threading form.
Example:
user=> (-> 84
(/ 4)
(as-> twenty-one ;; uses the value from ->
(* 2 twenty-one))) ;; no threading here
42
- clojure.core/some-> [expr & forms]
When expr is not nil, threads it into the first form (via ->), and when that result is not nil, through the next etc.
Example:
user=> (defn die [x] (assert false))
#'user/die
user=> (-> 1 inc range next next next die)
AssertionError Assert failed: false user/die (NO_SOURCE_FILE:65)
user=> (some-> 1 inc range next next next die)
nil
-
clojure.core/some->> [expr & forms]
When expr is not nil, threads it into the first form (via ->>), and when that result is not nil, through the next etc.
Same as some-> except the value is threaded as the last argument in each form.
- CLJ-960 Data read by the clojure reader is now tagged with :column in addition to :line.
- CLJ-745
It is now possible to expose protected final methods via
:exposes-methodsingen-class. This allows Clojure classes created via gen-class to access protected methods of its parent class.
Example:
(gen-class :name clojure.test_clojure.genclass.examples.ProtectedFinalTester
:extends java.lang.ClassLoader
:main false
:prefix "pf-"
:exposes-methods {findSystemClass superFindSystemClass})
- CLJ-948
It is now possible to annotate constructors via
gen-class.
Example:
(gen-class :name foo.Bar
:extends clojure.lang.Box
:constructors {^{Deprecated true} [Object] [Object]}
:init init
:prefix "foo")
- CLJ-966
defprotocolno longer requires that at least one method be given in the definition of the protocol. This allows for marker protocols, whose sole reason of existence is to allowsatisfies?to be true for a given type.
Example:
user=> (defprotocol P (hi [_]))
P
user=> (defprotocol M) ; marker protocol
M
user=> (deftype T [a] M P (hi [_] "hi there"))
user.T
user=> (satisfies? P (T. 1))
true
user=> (satisfies? M (T. 1))
true
user=> (hi (T. 1))
"hi there"
user=> (defprotocol M2 "marker for 2") ; marker protocol again
M2
user=> (extend-type T M2)
nil
user=> (satisfies? M2 (T. 1))
true
For the convenience of those that use Emacs Org mode,
clojure.pprint/print-table now prints tables in the form used by
that mode. Emacs Org mode has features to make it easy to edit such
tables, and even to do spreadsheet-like calculations on their
contents. See the Org mode documentation on
tables for details.
user=> (clojure.pprint/print-table [:name :initial-impression]
[{:name "Rich" :initial-impression "rock star"}
{:name "Andy" :initial-impression "engineer"}])
| :name | :initial-impression |
|-------+---------------------|
| Rich | rock star |
| Andy | engineer |
clojure.string/replace and clojure.string/replace-first are now
consistent in the way that they handle the replacement strings: all
characters in the replacement strings are treated literally, including
backslash and dollar sign characters.
user=> (require '[clojure.string :as s])
user=> (s/replace-first "munge.this" "." "$")
;=> "munge$this"
user=> (s/replace "/my/home/dir" #"/" (fn [s] "\\"))
;=> "\\my\\home\\dir"
There is one exception, which is described in the doc strings. If you
call these functions with a regex to search for and a string as the
replacement, then dollar sign and backslash characters in the
replacement string are treated specially. Occurrences of $1 in the
replacement string are replaced with the string that matched the first
parenthesized subexpression of the regex, occurrences of $2 are
replaced with the match of the second parenthesized subexpression,
etc.
user=> (s/replace "x12, b4" #"([a-z]+)([0-9]+)" "$1 <- $2")
;=> "x <- 12, b <- 4"
Individual occurrences of $ or \ in the replacement string that
you wish to be treated literally can be escaped by prefixing them with
a \. If you wish your replacement string to be treated literally
and its contents are unknown to you at compile time (or you don't wish
to tarnish your constant string with lots of backslashes), you can use
the new function clojure.string/re-quote-replacement to do the
necessary escaping of special characters for you.
user=> (s/replace "x12, b4" #"([a-z]+)([0-9]+)"
(s/re-quote-replacement "$1 <- $2"))
;=> "$1 <- $2, $1 <- $2"
All of the functions that construct sets such as set and
sorted-set allow duplicate elements to appear in their arguments,
and they are documented to treat this case as if by repeated uses of
conj.
Similarly, all map constructor functions such as hash-map,
array-map, and sorted-map allow duplicate keys, and are documented
to treat this case as if by repeated uses of assoc.
As before, literal sets, e.g. #{1 2 3}, do not allow duplicate
elements, and while elements can be expressions evaluated at run time
such as #{(inc x) (dec y)}, this leads to a check for duplicates at
run time whenever the set needs to be constructed, throwing an
exception if any duplicates are found.
Similarly, literal maps do not allow duplicate keys. New to Clojure 1.5 is a performance optimization: if all keys are compile time constants but one or more values are expressions requiring evaluation at run time, duplicate keys are checked for once at compile time only, not each time a map is constructed at run time.
- CLJ-1065 Allow duplicate set elements and map keys for all set and map constructors
Most functions that take a collection and return a "modified" version
of that collection preserve the metadata that was on the input
collection, e.g. conj, assoc, dissoc, etc. One notable
exception was into, which would return a collection with metadata
nil for several common types of input collections.
Now the functions into, select-keys, clojure.set/project, and
clojure.set/rename return collections with the same metadata as
their input collections.
- CLJ-988 Multimethod tables are now protected by a read/write lock instead of a synchronized method. This should result in a performance boost for multithreaded code using multimethods.
- CLJ-1061
when-firstnow evaluates its expression only once. - CLJ-1084
PersistentVector$ChunkedSeqnow implementsCountedinterface, to avoid some cases where vector elements were being counted by iterating over their elements. - CLJ-867 Records with same fields and field values, but different types, now usually hash to different values.
- CLJ-103 Improved if-let error message when form has a improperly defined body.
- CLJ-897 Don't use destructuring in defrecord/deftype arglists to get a slightly better error message when forgetting to specify the fields vector
- CLJ-788 Add source and line members and getters to CompilerException
- CLJ-157 Better error messages for syntax errors w/ defn and fn
- CLJ-940 Passing a non-sequence to refer :only results in uninformative exception
- CLJ-1024 Check for invalid varargs/destructuring uses.
- CLJ-1052
assocnow throws an exception if the last key argument is missing a value.
- CLJ-893 Document that vec will alias Java arrays
- CLJ-892 Clarify doc strings of sort and sort-by: they will modify Java array arguments
- CLJ-1019 ns-resolve doc has a typo
- CLJ-1038 Docstring for deliver doesn't match behavior
- CLJ-1055 "be come" should be "become"
- CLJ-917 clojure.core/definterface is not included in the API docs
- CLJ-962 Vectors returned by subvec allow access at negative indices
- CLJ-952 bigdec does not properly convert a clojure.lang.BigInt
- CLJ-975 inconsistent destructuring behaviour when using nested maps
- CLJ-954 TAP support in clojure.test.tap Needs Updating
- CLJ-881 exception when cl-format is given some ~f directive/value combinations
- CLJ-763 Do not check for duplicates in destructuring map creation
- CLJ-667 Allow loops fully nested in catch/finally
- CLJ-768 cl-format bug in ~f formatting
- CLJ-844 NPE calling keyword on map from bean
- CLJ-934 disj! Throws exception when attempting to remove multiple items in one call
- CLJ-943 When load-lib fails, a namespace is still created
- CLJ-981 clojure.set/rename-keys deletes keys when there's a collision
- CLJ-961 with-redefs loses a Var's root binding if the Var is thread-bound
- CLJ-1032 seque leaks threads from the send-off pool
- CLJ-1041 reduce-kv on sorted maps should stop on seeing a Reduced value
- CLJ-1011 clojure.data/diff should cope with null and false values in maps
- CLJ-977 (int \a) returns a value, (long \a) throws an exception
- CLJ-964 test-clojure/rt.clj has undeclared dependency on clojure.set
- CLJ-923 Reading ratios prefixed by + is not working
- CLJ-1012 partial function should also accept 1 arg (just f)
- CLJ-932 contains? Should throw exception on non-keyed collections
- CLJ-730 Create test suite for functional fns (e.g. juxt, comp, partial, etc.)
- CLJ-757 Empty transient maps/sets return wrong value for .contains
- CLJ-828 clojure.core/bases returns a cons when passed a class and a Java array when passed an interface
- CLJ-1062 CLJ-940 breaks compilation of namespaces that don't have any public functions
- CLJ-1070 PersistentQueue's hash function does not match its equality
- CLJ-987 pprint doesn't flush the underlying stream
- CLJ-963 Support pretty printing namespace declarations under code-dispatch
- CLJ-902 doc macro broken for namespaces
- CLJ-909 Make LineNumberingPushbackReader's buffer size configurable
- CLJ-910 Allow for type-hinting the method receiver in memfn
- CLJ-1048 add test.generative to Clojure's tests
- CLJ-1071 ExceptionInfo does no abstraction
- CLJ-1085 clojure.main/repl unconditionally refers REPL utilities into
*ns* - (no ticket) Rich Hickey fix: syntax-quote was walking records, returning maps