When a block given, iterates backwards over the elements of self, passing, in reverse order, each element to the block; returns self:
a = [] [0, 1, 2].reverse_each {|element| a.push(element) } a # => [2, 1, 0]
Allows the array to be modified during iteration:
a = ['a', 'b', 'c'] a.reverse_each {|element| a.clear if element.start_with?('b') } a # => []
When no block given, returns a new Enumerator.
Related: see Methods for Iterating.
With a block given, calls the block with each repeated permutation of length size of the elements of self; each permutation is an array; returns self. The order of the permutations is indeterminate.
If a positive integer argument size is given, calls the block with each size-tuple repeated permutation of the elements of self. The number of permutations is self.size**size.
Examples:
size is 1:
p = [] [0, 1, 2].repeated_permutation(1) {|permutation| p.push(permutation) } p # => [[0], [1], [2]]
size is 2:
p = [] [0, 1, 2].repeated_permutation(2) {|permutation| p.push(permutation) } p # => [[0, 0], [0, 1], [0, 2], [1, 0], [1, 1], [1, 2], [2, 0], [2, 1], [2, 2]]
If size is zero, calls the block once with an empty array.
If size is negative, does not call the block:
[0, 1, 2].repeated_permutation(-1) {|permutation| fail 'Cannot happen' }
With no block given, returns a new Enumerator.
Related: see Methods for Combining.
If object is an Integer object, returns object.
Integer.try_convert(1) # => 1
Otherwise if object responds to :to_int, calls object.to_int and returns the result.
Integer.try_convert(1.25) # => 1
Returns nil if object does not respond to :to_int
Integer.try_convert([]) # => nil
Raises an exception unless object.to_int returns an Integer object.
Attempts to convert the given object to a string.
If object is already a string, returns object, unmodified.
Otherwise if object responds to :to_str, calls object.to_str and returns the result.
Returns nil if object does not respond to :to_str.
Raises an exception unless object.to_str returns a string.
Returns an array of the grapheme clusters in self (see Unicode Grapheme Cluster Boundaries):
s = "\u0061\u0308-pqr-\u0062\u0308-xyz-\u0063\u0308" # => "ä-pqr-b̈-xyz-c̈" s.grapheme_clusters # => ["ä", "-", "p", "q", "r", "-", "b̈", "-", "x", "y", "z", "-", "c̈"]
Returns the next-larger representable Float.
These examples show the internally stored values (64-bit hexadecimal) for each Float f and for the corresponding f.next_float:
f = 0.0 # 0x0000000000000000 f.next_float # 0x0000000000000001 f = 0.01 # 0x3f847ae147ae147b f.next_float # 0x3f847ae147ae147c
In the remaining examples here, the output is shown in the usual way (result to_s):
0.01.next_float # => 0.010000000000000002 1.0.next_float # => 1.0000000000000002 100.0.next_float # => 100.00000000000001 f = 0.01 (0..3).each_with_index {|i| printf "%2d %-20a %s\n", i, f, f.to_s; f = f.next_float }
Output:
0 0x1.47ae147ae147bp-7 0.01
1 0x1.47ae147ae147cp-7 0.010000000000000002
2 0x1.47ae147ae147dp-7 0.010000000000000004
3 0x1.47ae147ae147ep-7 0.010000000000000005
f = 0.0; 100.times { f += 0.1 }
f # => 9.99999999999998 # should be 10.0 in the ideal world.
10-f # => 1.9539925233402755e-14 # the floating point error.
10.0.next_float-10 # => 1.7763568394002505e-15 # 1 ulp (unit in the last place).
(10-f)/(10.0.next_float-10) # => 11.0 # the error is 11 ulp.
(10-f)/(10*Float::EPSILON) # => 8.8 # approximation of the above.
"%a" % 10 # => "0x1.4p+3"
"%a" % f # => "0x1.3fffffffffff5p+3" # the last hex digit is 5. 16 - 5 = 11 ulp.
Related: Float#prev_float
Returns the next-smaller representable Float.
These examples show the internally stored values (64-bit hexadecimal) for each Float f and for the corresponding f.pev_float:
f = 5e-324 # 0x0000000000000001 f.prev_float # 0x0000000000000000 f = 0.01 # 0x3f847ae147ae147b f.prev_float # 0x3f847ae147ae147a
In the remaining examples here, the output is shown in the usual way (result to_s):
0.01.prev_float # => 0.009999999999999998 1.0.prev_float # => 0.9999999999999999 100.0.prev_float # => 99.99999999999999 f = 0.01 (0..3).each_with_index {|i| printf "%2d %-20a %s\n", i, f, f.to_s; f = f.prev_float }
Output:
0 0x1.47ae147ae147bp-7 0.01 1 0x1.47ae147ae147ap-7 0.009999999999999998 2 0x1.47ae147ae1479p-7 0.009999999999999997 3 0x1.47ae147ae1478p-7 0.009999999999999995
Related: Float#next_float.
Like backtrace, but returns each line of the execution stack as a Thread::Backtrace::Location. Accepts the same arguments as backtrace.
f = Fiber.new { Fiber.yield } f.resume loc = f.backtrace_locations.first loc.label #=> "yield" loc.path #=> "test.rb" loc.lineno #=> 1
Sets the Fiber scheduler for the current thread. If the scheduler is set, non-blocking fibers (created by Fiber.new with blocking: false, or by Fiber.schedule) call that scheduler’s hook methods on potentially blocking operations, and the current thread will call scheduler’s close method on finalization (allowing the scheduler to properly manage all non-finished fibers).
scheduler can be an object of any class corresponding to Fiber::Scheduler. Its implementation is up to the user.
See also the “Non-blocking fibers” section in class docs.
Returns the Fiber scheduler, that was last set for the current thread with Fiber.set_scheduler if and only if the current fiber is non-blocking.
Returns default external encoding.
The default external encoding is used by default for strings created from the following locations:
CSV
File data read from disk
SDBM
While strings created from these locations will have this encoding, the encoding may not be valid. Be sure to check String#valid_encoding?.
File data written to disk will be transcoded to the default external encoding when written, if default_internal is not nil.
The default external encoding is initialized by the -E option. If -E isn’t set, it is initialized to UTF-8 on Windows and the locale on other operating systems.
Sets default external encoding. You should not set Encoding::default_external in ruby code as strings created before changing the value may have a different encoding from strings created after the value was changed., instead you should use ruby -E to invoke ruby with the correct default_external.
See Encoding::default_external for information on how the default external encoding is used.
Returns default internal encoding. Strings will be transcoded to the default internal encoding in the following places if the default internal encoding is not nil:
CSV
File data read from disk
Strings returned from Readline
Strings returned from SDBM
Values from ENV
Values in ARGV including $PROGRAM_NAME
Additionally String#encode and String#encode! use the default internal encoding if no encoding is given.
The script encoding (__ENCODING__), not default_internal, is used as the encoding of created strings.
Encoding::default_internal is initialized with -E option or nil otherwise.
Sets default internal encoding or removes default internal encoding when passed nil. You should not set Encoding::default_internal in ruby code as strings created before changing the value may have a different encoding from strings created after the change. Instead you should use ruby -E to invoke ruby with the correct default_internal.
See Encoding::default_internal for information on how the default internal encoding is used.
Returns the locale charmap name. It returns nil if no appropriate information.
Debian GNU/Linux LANG=C Encoding.locale_charmap #=> "ANSI_X3.4-1968" LANG=ja_JP.EUC-JP Encoding.locale_charmap #=> "EUC-JP" SunOS 5 LANG=C Encoding.locale_charmap #=> "646" LANG=ja Encoding.locale_charmap #=> "eucJP"
The result is highly platform dependent. So Encoding.find(Encoding.locale_charmap) may cause an error. If you need some encoding object even for unknown locale, Encoding.find(“locale”) can be used.
Returns the message string with enhancements:
Includes the exception class name in the first line.
If the value of keyword highlight is true, includes bolding and underlining ANSI codes (see below) to enhance the appearance of the message.
Examples:
begin 1 / 0 rescue => x p x.message p x.detailed_message # Class name added. p x.detailed_message(highlight: true) # Class name, bolding, and underlining added. end
Output:
"divided by 0" "divided by 0 (ZeroDivisionError)" "\e[1mdivided by 0 (\e[1;4mZeroDivisionError\e[m\e[1m)\e[m"
This method is overridden by some gems in the Ruby standard library to add information:
An overriding method must be tolerant of passed keyword arguments, which may include (but may not be limited to):
:highlight.
:did_you_mean.
:error_highlight.
:syntax_suggest.
An overriding method should also be careful with ANSI code enhancements; see Messages.
Returns an enhanced message string:
Includes the exception class name.
If the value of keyword highlight is true (not nil or false), includes bolding ANSI codes (see below) to enhance the appearance of the message.
Includes the backtrace:
If the value of keyword order is :top (the default), lists the error message and the innermost backtrace entry first.
If the value of keyword order is :bottom, lists the error message the the innermost entry last.
Example:
def baz begin 1 / 0 rescue => x pp x.message pp x.full_message(highlight: false).split("\n") pp x.full_message.split("\n") end end def bar; baz; end def foo; bar; end foo
Output:
"divided by 0" ["t.rb:3:in 'Integer#/': divided by 0 (ZeroDivisionError)", "\tfrom t.rb:3:in 'Object#baz'", "\tfrom t.rb:10:in 'Object#bar'", "\tfrom t.rb:11:in 'Object#foo'", "\tfrom t.rb:12:in '<main>'"] ["t.rb:3:in 'Integer#/': \e[1mdivided by 0 (\e[1;4mZeroDivisionError\e[m\e[1m)\e[m", "\tfrom t.rb:3:in 'Object#baz'", "\tfrom t.rb:10:in 'Object#bar'", "\tfrom t.rb:11:in 'Object#foo'", "\tfrom t.rb:12:in '<main>'"]
An overriding method should be careful with ANSI code enhancements; see backtrace.
Returns the backtrace (the list of code locations that led to the exception), as an array of Thread::Backtrace::Location instances.
Example (assuming the code is stored in the file named t.rb):
def division(numerator, denominator) numerator / denominator end begin division(1, 0) rescue => ex p ex.backtrace_locations # ["t.rb:2:in 'Integer#/'", "t.rb:2:in 'Object#division'", "t.rb:6:in '<main>'"] loc = ex.backtrace_locations.first p loc.class # Thread::Backtrace::Location p loc.path # "t.rb" p loc.lineno # 2 p loc.label # "Integer#/" end
The value returned by this method might be adjusted when raising (see Kernel#raise), or during intermediate handling by set_backtrace.
See also backtrace that provide the same value as an array of strings. (Note though that two values might not be consistent with each other when backtraces are manually adjusted.)
See Backtraces.
Return a list of the local variable names defined where this NameError exception was raised.
Internal use only.
Creates instance variables and corresponding methods that return the value of each instance variable. Equivalent to calling “attr:name” on each name in turn. String arguments are converted to symbols. Returns an array of defined method names as symbols.
Creates an accessor method to allow assignment to the attribute symbol.id2name. String arguments are converted to symbols. Returns an array of defined method names as symbols.
Checks for a constant with the given name in mod. If inherit is set, the lookup will also search the ancestors (and Object if mod is a Module).
The value of the constant is returned if a definition is found, otherwise a NameError is raised.
Math.const_get(:PI) #=> 3.14159265358979
This method will recursively look up constant names if a namespaced class name is provided. For example:
module Foo; class Bar; end end Object.const_get 'Foo::Bar'
The inherit flag is respected on each lookup. For example:
module Foo class Bar VAL = 10 end class Baz < Bar; end end Object.const_get 'Foo::Baz::VAL' # => 10 Object.const_get 'Foo::Baz::VAL', false # => NameError
If the argument is not a valid constant name a NameError will be raised with a warning “wrong constant name”.
Object.const_get 'foobar' #=> NameError: wrong constant name foobar
Returns true if the arguments define a valid commercial date, false otherwise:
Date.valid_commercial?(2001, 5, 6) # => true Date.valid_commercial?(2001, 5, 8) # => false
See Date.commercial.
See argument start.
Related: Date.jd, Date.commercial.
Erases the line at the cursor corresponding to mode. mode may be either: 0: after cursor 1: before and cursor 2: entire line
You must require ‘io/console’ to use this method.
Erases the screen at the cursor corresponding to mode. mode may be either: 0: after cursor 1: before and cursor 2: entire screen
You must require ‘io/console’ to use this method.