When max is an Integer, rand returns a random integer greater than or equal to zero and less than max. Unlike Kernel.rand, when max is a negative integer or zero, rand raises an ArgumentError.
prng = Random.new prng.rand(100) # => 42
When max is a Float, rand returns a random floating point number between 0.0 and max, including 0.0 and excluding max.
prng.rand(1.5) # => 1.4600282860034115
When max is a Range, rand returns a random number where range.member?(number) == true.
prng.rand(5..9) # => one of [5, 6, 7, 8, 9] prng.rand(5...9) # => one of [5, 6, 7, 8] prng.rand(5.0..9.0) # => between 5.0 and 9.0, including 9.0 prng.rand(5.0...9.0) # => between 5.0 and 9.0, excluding 9.0
Both the beginning and ending values of the range must respond to subtract (-) and add (+)methods, or rand will raise an ArgumentError.
Seeds the system pseudo-random number generator, Random::DEFAULT, with number. The previous seed value is returned.
If number is omitted, seeds the generator using a source of entropy provided by the operating system, if available (/dev/urandom on Unix systems or the RSA cryptographic provider on Windows), which is then combined with the time, the process id, and a sequence number.
srand may be used to ensure repeatable sequences of pseudo-random numbers between different runs of the program. By setting the seed to a known value, programs can be made deterministic during testing.
srand 1234 # => 268519324636777531569100071560086917274 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319] [ rand(10), rand(1000) ] # => [4, 664] srand 1234 # => 1234 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319]
Alias of Random::DEFAULT.rand.
A convenience method for TracePoint.new, that activates the trace automatically.
trace = TracePoint.trace(:call) { |tp| [tp.lineno, tp.event] } #=> #<TracePoint:enabled> trace.enabled? #=> true
Line number of the event
Displays each of the given messages followed by a record separator on STDERR unless warnings have been disabled (for example with the -W0 flag).
warn("warning 1", "warning 2")
<em>produces:</em>
warning 1
warning 2
With no arguments, raises the exception in $! or raises a RuntimeError if $! is nil. With a single String argument, raises a RuntimeError with the string as a message. Otherwise, the first parameter should be the name of an Exception class (or an object that returns an Exception object when sent an exception message). The optional second parameter sets the message associated with the exception, and the third parameter is an array of callback information. Exceptions are caught by the rescue clause of begin...end blocks.
raise "Failed to create socket" raise ArgumentError, "No parameters", caller
Equivalent to Kernel::gets, except readline raises EOFError at end of file.
Returns an array containing the lines returned by calling Kernel.gets(sep) until the end of file.
Seeds the system pseudo-random number generator, Random::DEFAULT, with number. The previous seed value is returned.
If number is omitted, seeds the generator using a source of entropy provided by the operating system, if available (/dev/urandom on Unix systems or the RSA cryptographic provider on Windows), which is then combined with the time, the process id, and a sequence number.
srand may be used to ensure repeatable sequences of pseudo-random numbers between different runs of the program. By setting the seed to a known value, programs can be made deterministic during testing.
srand 1234 # => 268519324636777531569100071560086917274 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319] [ rand(10), rand(1000) ] # => [4, 664] srand 1234 # => 1234 [ rand, rand ] # => [0.1915194503788923, 0.6221087710398319]
If called without an argument, or if max.to_i.abs == 0, rand returns a pseudo-random floating point number between 0.0 and 1.0, including 0.0 and excluding 1.0.
rand #=> 0.2725926052826416
When max.abs is greater than or equal to 1, rand returns a pseudo-random integer greater than or equal to 0 and less than max.to_i.abs.
rand(100) #=> 12
When max is a Range, rand returns a random number where range.member?(number) == true.
Negative or floating point values for max are allowed, but may give surprising results.
rand(-100) # => 87 rand(-0.5) # => 0.8130921818028143 rand(1.9) # equivalent to rand(1), which is always 0
Kernel.srand may be used to ensure that sequences of random numbers are reproducible between different runs of a program.
See also Random.rand.
Returns x/y;
Rational(1, 2) #=> (1/2) Rational('1/2') #=> (1/2) Rational(nil) #=> TypeError Rational(1, nil) #=> TypeError
Syntax of 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 String#to_r.
Specifies the handling of signals. The first parameter is a signal name (a string such as “SIGALRM”, “SIGUSR1”, and so on) or a signal number. The characters “SIG” may be omitted from the signal name. The command or block specifies code to be run when the signal is raised. If the command is the string “IGNORE” or “SIG_IGN”, the signal will be ignored. If the command is “DEFAULT” or “SIG_DFL”, the Ruby’s default handler will be invoked. If the command is “EXIT”, the script will be terminated by the signal. If the command is “SYSTEM_DEFAULT”, the operating system’s default handler will be invoked. Otherwise, the given command or block will be run. The special signal name “EXIT” or signal number zero will be invoked just prior to program termination. trap returns the previous handler for the given signal.
Signal.trap(0, proc { puts "Terminating: #{$$}" }) Signal.trap("CLD") { puts "Child died" } fork && Process.wait
produces:
Terminating: 27461 Child died Terminating: 27460
Returns true if yield would execute a block in the current context. The iterator? form is mildly deprecated.
def try if block_given? yield else "no block" end end try #=> "no block" try { "hello" } #=> "hello" try do "hello" end #=> "hello"
Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.
If no block is given, an enumerator is returned instead.
(1..6).partition { |v| v.even? } #=> [[2, 4, 6], [1, 3, 5]]
Passes each element of the collection to the given block. The method returns true if the block returns true exactly once. If the block is not given, one? will return true only if exactly one of the collection members is true.
%w{ant bear cat}.one? { |word| word.length == 4 } #=> true %w{ant bear cat}.one? { |word| word.length > 4 } #=> false %w{ant bear cat}.one? { |word| word.length < 4 } #=> false [ nil, true, 99 ].one? #=> false [ nil, true, false ].one? #=> true
Passes each element of the collection to the given block. The method returns true if the block never returns true for all elements. If the block is not given, none? will return true only if none of the collection members is true.
%w{ant bear cat}.none? { |word| word.length == 5 } #=> true %w{ant bear cat}.none? { |word| word.length >= 4 } #=> false [].none? #=> true [nil].none? #=> true [nil, false].none? #=> true [nil, false, true].none? #=> false
Enables coverage measurement.
Returns a memory pointer of a function’s hexadecimal address location val
Example:
lib = Fiddle.dlopen('/lib64/libc-2.15.so')
=> #<Fiddle::Handle:0x00000001342460>
Fiddle.dlwrap(lib['strcpy'].to_s(16))
=> 25522520
Returns the hexadecimal representation of a memory pointer address addr
Example:
lib = Fiddle.dlopen('/lib64/libc-2.15.so')
=> #<Fiddle::Handle:0x00000001342460>
lib['strcpy'].to_s(16)
=> "7f59de6dd240"
Fiddle.dlunwrap(Fiddle.dlwrap(lib['strcpy'].to_s(16)))
=> "7f59de6dd240"
Parse the JSON document source into a Ruby data structure and return it.
opts can have the following keys:
max_nesting: The maximum depth of nesting allowed in the parsed data structures. Disable depth checking with :max_nesting => false. It defaults to 100.
allow_nan: If set to true, allow NaN, Infinity and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to false.
symbolize_names: If set to true, returns symbols for the names (keys) in a JSON object. Otherwise strings are returned. Strings are the default.
create_additions: If set to false, the Parser doesn’t create additions even if a matching class and create_id was found. This option defaults to false.
object_class: Defaults to Hash
array_class: Defaults to Array
Parse the JSON document source into a Ruby data structure and return it. The bang version of the parse method defaults to the more dangerous values for the opts hash, so be sure only to parse trusted source documents.
opts can have the following keys:
max_nesting: The maximum depth of nesting allowed in the parsed data structures. Enable depth checking with :max_nesting => anInteger. The parse! methods defaults to not doing max depth checking: This can be dangerous if someone wants to fill up your stack.
allow_nan: If set to true, allow NaN, Infinity, and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to true.
create_additions: If set to false, the Parser doesn’t create additions even if a matching class and create_id was found. This option defaults to false.
See any remaining errors held in queue.
Any errors you see here are probably due to a bug in ruby’s OpenSSL implementation.
Parse a YAML string in yaml. Returns the Psych::Nodes::Document. filename is used in the exception message if a Psych::SyntaxError is raised.
Raises a Psych::SyntaxError when a YAML syntax error is detected.
Example:
Psych.parse("---\n - a\n - b") # => #<Psych::Nodes::Document:0x00> begin Psych.parse("--- `", "file.txt") rescue Psych::SyntaxError => ex ex.file # => 'file.txt' ex.message # => "(file.txt): found character that cannot start any token" end
See Psych::Nodes for more information about YAML AST.