Returns the previous representable floating point number.
(-Float::MAX).prev_float and (-Float::INFINITY).prev_float is -Float::INFINITY.
Float::NAN.prev_float is Float::NAN.
For example:
0.01.prev_float #=> 0.009999999999999998 1.0.prev_float #=> 0.9999999999999999 100.0.prev_float #=> 99.99999999999999 0.01 - 0.01.prev_float #=> 1.734723475976807e-18 1.0 - 1.0.prev_float #=> 1.1102230246251565e-16 100.0 - 100.0.prev_float #=> 1.4210854715202004e-14 f = 0.01; 20.times { printf "%-20a %s\n", f, f.to_s; f = f.prev_float } #=> 0x1.47ae147ae147bp-7 0.01 # 0x1.47ae147ae147ap-7 0.009999999999999998 # 0x1.47ae147ae1479p-7 0.009999999999999997 # 0x1.47ae147ae1478p-7 0.009999999999999995 # 0x1.47ae147ae1477p-7 0.009999999999999993 # 0x1.47ae147ae1476p-7 0.009999999999999992 # 0x1.47ae147ae1475p-7 0.00999999999999999 # 0x1.47ae147ae1474p-7 0.009999999999999988 # 0x1.47ae147ae1473p-7 0.009999999999999986 # 0x1.47ae147ae1472p-7 0.009999999999999985 # 0x1.47ae147ae1471p-7 0.009999999999999983 # 0x1.47ae147ae147p-7 0.009999999999999981 # 0x1.47ae147ae146fp-7 0.00999999999999998 # 0x1.47ae147ae146ep-7 0.009999999999999978 # 0x1.47ae147ae146dp-7 0.009999999999999976 # 0x1.47ae147ae146cp-7 0.009999999999999974 # 0x1.47ae147ae146bp-7 0.009999999999999972 # 0x1.47ae147ae146ap-7 0.00999999999999997 # 0x1.47ae147ae1469p-7 0.009999999999999969 # 0x1.47ae147ae1468p-7 0.009999999999999967
Returns the path parameter passed to dir’s constructor.
d = Dir.new("..") d.path #=> ".."
Returns the pathname used to create file as a string. Does not normalize the name.
The pathname may not point to the file corresponding to file. For instance, the pathname becomes void when the file has been moved or deleted.
This method raises IOError for a file created using File::Constants::TMPFILE because they don’t have a pathname.
File.new("testfile").path #=> "testfile" File.new("/tmp/../tmp/xxx", "w").path #=> "/tmp/../tmp/xxx"
Returns true if the named file is writable by the real user and group id of this process. See access(3).
Note that some OS-level security features may cause this to return true even though the file is not writable by the real user/group.
If file_name is writable by others, returns an integer representing the file permission bits of file_name. Returns nil otherwise. The meaning of the bits is platform dependent; on Unix systems, see stat(2).
file_name can be an IO object.
File.world_writable?("/tmp") #=> 511 m = File.world_writable?("/tmp") sprintf("%o", m) #=> "777"
Returns true if the named file is executable by the real user and group id of this process. See access(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 real user/group.
Returns the list of available encoding names.
Encoding.name_list
#=> ["US-ASCII", "ASCII-8BIT", "UTF-8",
"ISO-8859-1", "Shift_JIS", "EUC-JP",
"Windows-31J",
"BINARY", "CP932", "eucJP"]
Returns true if exception messages will be sent to a tty.
Deserializes JSON string by constructing new Exception object with message m and backtrace b serialized with to_json
When this module is included in another, Ruby calls append_features in this module, passing it the receiving module in mod. Ruby’s default implementation is to add the constants, methods, and module variables of this module to mod if this module has not already been added to mod or one of its ancestors. See also Module#include.
Callback invoked whenever the receiver is included in another module or class. This should be used in preference to Module.append_features if your code wants to perform some action when a module is included in another.
module A def A.included(mod) puts "#{self} included in #{mod}" end end module Enumerable include A end # => prints "A included in Enumerable"
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.
Defines a named attribute for this module, where the name is symbol.id2name, creating an instance variable (@name) and a corresponding access method to read it. Also creates a method called name= to set the attribute. String arguments are converted to symbols.
module Mod attr_accessor(:one, :two) end Mod.instance_methods.sort #=> [:one, :one=, :two, :two=]
Returns an array containing the names of the public and protected instance methods in the receiver. For a module, these are the public and protected methods; for a class, they are the instance (not singleton) methods. If the optional parameter is false, the methods of any ancestors are not included.
module A def method1() end end class B include A def method2() end end class C < B def method3() end end A.instance_methods(false) #=> [:method1] B.instance_methods(false) #=> [:method2] B.instance_methods(true).include?(:method1) #=> true C.instance_methods(false) #=> [:method3] C.instance_methods.include?(:method2) #=> true
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
Sets the named constant to the given object, returning that object. Creates a new constant if no constant with the given name previously existed.
Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0) #=> 3.14285714285714 Math::HIGH_SCHOOL_PI - Math::PI #=> 0.00126448926734968
If sym or str is not a valid constant name a NameError will be raised with a warning “wrong constant name”.
Object.const_set('foobar', 42) #=> NameError: wrong constant name foobar
Says whether mod or its ancestors have a constant with the given name:
Float.const_defined?(:EPSILON) #=> true, found in Float itself Float.const_defined?("String") #=> true, found in Object (ancestor) BasicObject.const_defined?(:Hash) #=> false
If mod is a Module, additionally Object and its ancestors are checked:
Math.const_defined?(:String) #=> true, found in Object
In each of the checked classes or modules, if the constant is not present but there is an autoload for it, true is returned directly without autoloading:
module Admin autoload :User, 'admin/user' end Admin.const_defined?(:User) #=> true
If the constant is not found the callback const_missing is not called and the method returns false.
If inherit is false, the lookup only checks the constants in the receiver:
IO.const_defined?(:SYNC) #=> true, found in File::Constants (ancestor) IO.const_defined?(:SYNC, false) #=> false, not found in IO itself
In this case, the same logic for autoloading applies.
If the argument is not a valid constant name a NameError is raised with the message “wrong constant name name”:
Hash.const_defined? 'foobar' #=> NameError: wrong constant name foobar
Invoked when a reference is made to an undefined constant in mod. It is passed a symbol for the undefined constant, and returns a value to be used for that constant. The following code is an example of the same:
def Foo.const_missing(name) name # return the constant name as Symbol end Foo::UNDEFINED_CONST #=> :UNDEFINED_CONST: symbol returned
In the next example when a reference is made to an undefined constant, it attempts to load a file whose name is the lowercase version of the constant (thus class Fred is assumed to be in file fred.rb). If found, it returns the loaded class. It therefore implements an autoload feature similar to Kernel#autoload and Module#autoload.
def Object.const_missing(name) @looked_for ||= {} str_name = name.to_s raise "Class not found: #{name}" if @looked_for[str_name] @looked_for[str_name] = 1 file = str_name.downcase require file klass = const_get(name) return klass if klass raise "Class not found: #{name}" end
Makes a list of existing constants public.
Makes a list of existing constants private.
Returns true if mod is a singleton class or false if it is an ordinary class or module.
class C end C.singleton_class? #=> false C.singleton_class.singleton_class? #=> true
Returns an UnboundMethod representing the given instance method in mod.
class Interpreter def do_a() print "there, "; end def do_d() print "Hello "; end def do_e() print "!\n"; end def do_v() print "Dave"; end Dispatcher = { "a" => instance_method(:do_a), "d" => instance_method(:do_d), "e" => instance_method(:do_e), "v" => instance_method(:do_v) } def interpret(string) string.each_char {|b| Dispatcher[b].bind(self).call } end end interpreter = Interpreter.new interpreter.interpret('dave')
produces:
Hello there, Dave!
Removes the method identified by symbol from the current class. For an example, see Module#undef_method. String arguments are converted to symbols.
For the given method names, marks the method as passing keywords through a normal argument splat. This should only be called on methods that accept an argument splat (*args) but not explicit keywords or a keyword splat. It marks the method such that if the method is called with keyword arguments, the final hash argument is marked with a special flag such that if it is the final element of a normal argument splat to another method call, and that method call does not include explicit keywords or a keyword splat, the final element is interpreted as keywords. In other words, keywords will be passed through the method to other methods.
This should only be used for methods that delegate keywords to another method, and only for backwards compatibility with Ruby versions before 2.7.
This method will probably be removed at some point, as it exists only for backwards compatibility. As it does not exist in Ruby versions before 2.7, check that the module responds to this method before calling it. Also, be aware that if this method is removed, the behavior of the method will change so that it does not pass through keywords.
module Mod def foo(meth, *args, &block) send(:"do_#{meth}", *args, &block) end ruby2_keywords(:foo) if respond_to?(:ruby2_keywords, true) end