Returns true
if a Proc
object is lambda. false
if non-lambda.
The lambda-ness affects argument handling and the behavior of return
and break
.
A Proc
object generated by proc
ignores extra arguments.
proc {|a,b| [a,b] }.call(1,2,3) #=> [1,2]
It provides nil
for missing arguments.
proc {|a,b| [a,b] }.call(1) #=> [1,nil]
It expands a single array argument.
proc {|a,b| [a,b] }.call([1,2]) #=> [1,2]
A Proc
object generated by lambda
doesn’t have such tricks.
lambda {|a,b| [a,b] }.call(1,2,3) #=> ArgumentError lambda {|a,b| [a,b] }.call(1) #=> ArgumentError lambda {|a,b| [a,b] }.call([1,2]) #=> ArgumentError
Proc#lambda?
is a predicate for the tricks. It returns true
if no tricks apply.
lambda {}.lambda? #=> true proc {}.lambda? #=> false
Proc.new
is the same as proc
.
Proc.new {}.lambda? #=> false
lambda
, proc
and Proc.new
preserve the tricks of a Proc
object given by &
argument.
lambda(&lambda {}).lambda? #=> true proc(&lambda {}).lambda? #=> true Proc.new(&lambda {}).lambda? #=> true lambda(&proc {}).lambda? #=> false proc(&proc {}).lambda? #=> false Proc.new(&proc {}).lambda? #=> false
A Proc
object generated by &
argument has the tricks
def n(&b) b.lambda? end n {} #=> false
The &
argument preserves the tricks if a Proc
object is given by &
argument.
n(&lambda {}) #=> true n(&proc {}) #=> false n(&Proc.new {}) #=> false
A Proc
object converted from a method has no tricks.
def m() end method(:m).to_proc.lambda? #=> true n(&method(:m)) #=> true n(&method(:m).to_proc) #=> true
define_method
is treated the same as method definition. The defined method has no tricks.
class C define_method(:d) {} end C.new.d(1,2) #=> ArgumentError C.new.method(:d).to_proc.lambda? #=> true
define_method
always defines a method without the tricks, even if a non-lambda Proc
object is given. This is the only exception for which the tricks are not preserved.
class C define_method(:e, &proc {}) end C.new.e(1,2) #=> ArgumentError C.new.method(:e).to_proc.lambda? #=> true
This exception ensures that methods never have tricks and makes it easy to have wrappers to define methods that behave as usual.
class C def self.def2(name, &body) define_method(name, &body) end def2(:f) {} end C.new.f(1,2) #=> ArgumentError
The wrapper def2 defines a method which has no tricks.
Take a message from ractor’s outgoing port, which was put there by Ractor.yield
or at ractor’s finalization.
r = Ractor.new do Ractor.yield 'explicit yield' 'last value' end puts r.take #=> 'explicit yield' puts r.take #=> 'last value' puts r.take # Ractor::ClosedError (The outgoing-port is already closed)
The fact that the last value is also put to outgoing port means that take
can be used as some analog of Thread#join
(“just wait till ractor finishes”), but don’t forget it will raise if somebody had already consumed everything ractor have produced.
If the outgoing port was closed with close_outgoing
, the method will raise Ractor::ClosedError
.
r = Ractor.new do sleep(500) Ractor.yield 'Hello from ractor' end r.close_outgoing r.take # Ractor::ClosedError (The outgoing-port is already closed) # The error would be raised immediately, not when ractor will try to receive
If an uncaught exception is raised in the Ractor
, it is propagated on take as a Ractor::RemoteError
.
r = Ractor.new {raise "Something weird happened"} begin r.take rescue => e p e # => #<Ractor::RemoteError: thrown by remote Ractor.> p e.ractor == r # => true p e.cause # => #<RuntimeError: Something weird happened> end
Ractor::ClosedError
is a descendant of StopIteration
, so the closing of the ractor will break the loops without propagating the error:
r = Ractor.new do 3.times {|i| Ractor.yield "message #{i}"} "finishing" end loop {puts "Received: " + r.take} puts "Continue successfully"
This will print:
Received: message 0 Received: message 1 Received: message 2 Received: finishing Continue successfully
Basically the same as ::new
. However, if class Thread
is subclassed, then calling start
in that subclass will not invoke the subclass’s initialize
method.
Terminates thr
and schedules another thread to be run, returning the terminated Thread
. If this is the main thread, or the last thread, exits the process.
Path of the file being run
Return the tag object which was called for.
Creates a new Pathname
object from the given string, path
, and returns pathname object.
In order to use this constructor, you must first require the Pathname
standard library extension.
require 'pathname' Pathname("/home/zzak") #=> #<Pathname:/home/zzak>
See also Pathname::new
for more information.
Yields self to the block, and then returns self. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.
(1..10) .tap {|x| puts "original: #{x}" } .to_a .tap {|x| puts "array: #{x}" } .select {|x| x.even? } .tap {|x| puts "evens: #{x}" } .map {|x| x*x } .tap {|x| puts "squares: #{x}" }
Returns arg converted to a float. Numeric
types are converted directly, and with exception to String
and nil
the rest are converted using arg.to_f
. Converting a String
with invalid characters will result in a ArgumentError
. Converting nil
generates a TypeError
. Exceptions can be suppressed by passing exception: false
.
Float(1) #=> 1.0 Float("123.456") #=> 123.456 Float("123.0_badstring") #=> ArgumentError: invalid value for Float(): "123.0_badstring" Float(nil) #=> TypeError: can't convert nil into Float Float("123.0_badstring", exception: false) #=> nil
Returns the string resulting from formatting objects
into format_string
.
For details on format_string
, see Format Specifications.
Kernel#format
is an alias for Kernel#sprintf
.
Equivalent to Proc.new
, except the resulting Proc
objects check the number of parameters passed when called.
Returns x/y
or arg
as a Rational
.
Rational(2, 3) #=> (2/3) Rational(5) #=> (5/1) Rational(0.5) #=> (1/2) Rational(0.3) #=> (5404319552844595/18014398509481984) Rational("2/3") #=> (2/3) Rational("0.3") #=> (3/10) Rational("10 cents") #=> ArgumentError Rational(nil) #=> TypeError Rational(1, nil) #=> TypeError Rational("10 cents", exception: false) #=> nil
Syntax of the string form:
string form = extra spaces , rational , extra spaces ; rational = [ sign ] , unsigned rational ; unsigned rational = numerator | numerator , "/" , denominator ; numerator = integer part | fractional part | integer part , fractional part ; denominator = digits ; integer part = digits ; fractional part = "." , digits , [ ( "e" | "E" ) , [ sign ] , digits ] ; sign = "-" | "+" ; digits = digit , { digit | "_" , digit } ; digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ; extra spaces = ? \s* ? ;
See also String#to_r
.
Deprecated. Use block_given? instead.
catch
executes its block. If throw
is not called, the block executes normally, and catch
returns the value of the last expression evaluated.
catch(1) { 123 } # => 123
If throw(tag2, val)
is called, Ruby searches up its stack for a catch
block whose tag
has the same object_id
as tag2. When found, the block stops executing and returns val (or nil
if no second argument was given to throw
).
catch(1) { throw(1, 456) } # => 456 catch(1) { throw(1) } # => nil
When tag
is passed as the first argument, catch
yields it as the parameter of the block.
catch(1) {|x| x + 2 } # => 3
When no tag
is given, catch
yields a new unique object (as from Object.new
) as the block parameter. This object can then be used as the argument to throw
, and will match the correct catch
block.
catch do |obj_A| catch do |obj_B| throw(obj_B, 123) puts "This puts is not reached" end puts "This puts is displayed" 456 end # => 456 catch do |obj_A| catch do |obj_B| throw(obj_A, 123) puts "This puts is still not reached" end puts "Now this puts is also not reached" 456 end # => 123
Returns a hash containing the counts of equal elements:
Each key is an element of self
.
Each value is the number elements equal to that key.
With no argument:
%w[a b c b c a c b].tally # => {"a"=>2, "b"=>3, "c"=>3}
With a hash argument, that hash is used for the tally (instead of a new hash), and is returned; this may be useful for accumulating tallies across multiple enumerables:
hash = {} hash = %w[a c d b c a].tally(hash) hash # => {"a"=>2, "c"=>2, "d"=>1, "b"=>1} hash = %w[b a z].tally(hash) hash # => {"a"=>3, "c"=>2, "d"=>1, "b"=>2, "z"=>1} hash = %w[b a m].tally(hash) hash # => {"a"=>4, "c"=>2, "d"=>1, "b"=>3, "z"=>1, "m"=> 1}
For non-negative integer n
, returns the first n
elements:
r = (1..4) r.take(2) # => [1, 2] r.take(0) # => [] h = {foo: 0, bar: 1, baz: 2, bat: 3} h.take(2) # => [[:foo, 0], [:bar, 1]]
Enables the coverage measurement. See the documentation of Coverage
class in detail. This is equivalent to Coverage.setup
and Coverage.resume
.
Returns a String containing the generated JSON data.
See also JSON.fast_generate
, JSON.pretty_generate
.
Argument obj
is the Ruby object to be converted to JSON.
Argument opts
, if given, contains a Hash of options for the generation. See Generating Options.
When obj
is an Array, returns a String containing a JSON array:
obj = ["foo", 1.0, true, false, nil] json = JSON.generate(obj) json # => '["foo",1.0,true,false,null]'
When obj
is a Hash, returns a String containing a JSON object:
obj = {foo: 0, bar: 's', baz: :bat} json = JSON.generate(obj) json # => '{"foo":0,"bar":"s","baz":"bat"}'
For examples of generating from other Ruby objects, see Generating JSON from Other Objects.
Raises an exception if any formatting option is not a String.
Raises an exception if obj
contains circular references:
a = []; b = []; a.push(b); b.push(a) # Raises JSON::NestingError (nesting of 100 is too deep): JSON.generate(a)
Returns self, for backward compatibility.
Compresses the given string
. Valid values of level are Zlib::NO_COMPRESSION
, Zlib::BEST_SPEED
, Zlib::BEST_COMPRESSION
, Zlib::DEFAULT_COMPRESSION
, or an integer from 0 to 9.
This method is almost equivalent to the following code:
def deflate(string, level) z = Zlib::Deflate.new(level) dst = z.deflate(string, Zlib::FINISH) z.close dst end
See also Zlib.inflate
Decompresses string
. Raises a Zlib::NeedDict
exception if a preset dictionary is needed for decompression.
This method is almost equivalent to the following code:
def inflate(string) zstream = Zlib::Inflate.new buf = zstream.inflate(string) zstream.finish zstream.close buf end
See also Zlib.deflate
Returns true
if the named file is readable by the effective user and group id of this process. See eaccess(3).
Note that some OS-level security features may cause this to return true even though the file is not readable by the effective user/group.
Returns true
if the named file is writable by the effective user and group id of this process. See eaccess(3).
Note that some OS-level security features may cause this to return true even though the file is not writable by the effective user/group.
Returns true
if the named file is executable by the effective user and group id of this process. See eaccess(3).
Windows does not support execute permissions separately from read permissions. On Windows, a file is only considered executable if it ends in .bat, .cmd, .com, or .exe.
Note that some OS-level security features may cause this to return true even though the file is not executable by the effective user/group.
Initiates garbage collection, even if manually disabled.
This method is defined with keyword arguments that default to true:
def GC.start(full_mark: true, immediate_sweep: true); end
Use full_mark: false to perform a minor GC. Use immediate_sweep: false to defer sweeping (use lazy sweep).
Note: These keyword arguments are implementation and version dependent. They are not guaranteed to be future-compatible, and may be ignored if the underlying implementation does not support them.