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# -*- rdoc -*-

= NEWS for Ruby 2.4.0

This document is a list of user visible feature changes made between
releases except for bug fixes.

Note that each entry is kept so brief that no reason behind or
reference information is supplied with.  For a full list of changes
with all sufficient information, see the ChangeLog file or Redmine
(e.g. <tt>https://bugs.ruby-lang.org/issues/$FEATURE_OR_BUG_NUMBER</tt>)

== Changes since the 2.3.0 release

=== Language changes

* Multiple assignment in conditional expression is now allowed.
  [Feature #10617]

=== Core classes updates (outstanding ones only)

* Array

  * Array#max and Array#min.  [Feature #12172]
    This may cause a tiny incompatibility: if you redefine
    Enumerable#max and call max to an Array, your redefinition will be
    now ignored.  You should also redefine Array#max.

  * Array#sum  [Feature #12217]

* Dir

  * Dir.empty?.  [Feature #10121]

* File

  * File.empty?.  [Feature #9969]

* Float

  * Float#ceil, Float#floor, and Float#truncate now take an optional
    digits, as well as Float#round.  [Feature #12245]

* Integer

  * Integer#ceil, Integer#floor, and Integer#truncate now take an optional
    digits, as well as Integer#round.  [Feature #12245]

* String

  * String.new(capacity: size) [Feature #12024]

* Symbol

  * Symbol#match now returns MatchData.  [Bug #11991]

* MatchData

  * MatchData#named_captures [Feature #11999]

=== Stdlib updates (outstanding ones only)

* CSV

  * Add a liberal_parsing option. [Feature #11839]

* Logger

	* Allow specifying logger parameters in constructor such
	  as level, progname, datetime_format, formatter. [Feature #12224]
	* Add shift_period_suffix option. [Feature #10772]

* optparse

  * Add an into option. [Feature #11191]

=== Compatibility issues (excluding feature bug fixes)

* Array#sum is implemented.  Ruby itself has no compatibility problem
  because Ruby didn't have sum method for arrays before Ruby 2.4.
  However many third party gems, activesupport, facets, simple_stats, etc,
  defines sum method.  These implementations are mostly compatible but
  there are subtle differences.
  Ruby's sum method should be mostly compatible but it is impossible to
  be perfectly compatible with all of them.

=== Stdlib compatibility issues (excluding feature bug fixes)

* DateTime

  * DateTime#to_time now preserves timezone.  [Bug #12189]

=== C API updates

* ruby_show_version() will no longer exits the process, if
  RUBY_SHOW_COPYRIGHT_TO_DIE is set to 0.  This will be the default in
  the future.

=== Supported platform changes

=== Implementation improvements

* In some condition, `[x, y].max` and `[x, y].min` are optimized
  so that a temporal array is not created.  The concrete condition is
  an implementation detail: currently, the array literal must have no
  splat, must have at least one expression but literal, the length must
  be <= 0x100, and Array#max and min must not be redefined.  It will work
  in most casual and real-life use case where it is written with intent
  to `Math.max(x, y)`.