A complex number can be represented as a paired real number with imaginary unit; a+bi. Where a is real part, b is imaginary part and i is imaginary unit. Real a equals complex a+0i mathematically.
Complex object can be created as literal, and also by using Kernel#Complex, Complex::rect, Complex::polar or to_c method.
2+1i #=> (2+1i) Complex(1) #=> (1+0i) Complex(2, 3) #=> (2+3i) Complex.polar(2, 3) #=> (-1.9799849932008908+0.2822400161197344i) 3.to_c #=> (3+0i)
You can also create complex object from floating-point numbers or strings.
Complex(0.3) #=> (0.3+0i) Complex('0.3-0.5i') #=> (0.3-0.5i) Complex('2/3+3/4i') #=> ((2/3)+(3/4)*i) Complex('1@2') #=> (-0.4161468365471424+0.9092974268256817i) 0.3.to_c #=> (0.3+0i) '0.3-0.5i'.to_c #=> (0.3-0.5i) '2/3+3/4i'.to_c #=> ((2/3)+(3/4)*i) '1@2'.to_c #=> (-0.4161468365471424+0.9092974268256817i)
A complex object is either an exact or an inexact number.
Complex(1, 1) / 2 #=> ((1/2)+(1/2)*i) Complex(1, 1) / 2.0 #=> (0.5+0.5i)
A File is an abstraction of any file object accessible by the program and is closely associated with class IO. File includes the methods of module FileTest as class methods, allowing you to write (for example) File.exist?("foo").
In the description of File methods, permission bits are a platform-specific set of bits that indicate permissions of a file. On Unix-based systems, permissions are viewed as a set of three octets, for the owner, the group, and the rest of the world. For each of these entities, permissions may be set to read, write, or execute the file:
The permission bits 0644 (in octal) would thus be interpreted as read/write for owner, and read-only for group and other. Higher-order bits may also be used to indicate the type of file (plain, directory, pipe, socket, and so on) and various other special features. If the permissions are for a directory, the meaning of the execute bit changes; when set the directory can be searched.
On non-Posix operating systems, there may be only the ability to make a file read-only or read-write. In this case, the remaining permission bits will be synthesized to resemble typical values. For instance, on Windows NT the default permission bits are 0644, which means read/write for owner, read-only for all others. The only change that can be made is to make the file read-only, which is reported as 0444.
Various constants for the methods in File can be found in File::Constants.
Raised when a method is called on a receiver which doesn’t have it defined and also fails to respond with method_missing.
"hello".to_ary
raises the exception:
NoMethodError: undefined method `to_ary' for "hello":String
Raised when memory allocation fails.
SystemCallError is the base class for all low-level platform-dependent errors.
The errors available on the current platform are subclasses of SystemCallError and are defined in the Errno module.
File.open("does/not/exist")
raises the exception:
Errno::ENOENT: No such file or directory - does/not/exist
WIN32OLE objects represent OLE Automation object in Ruby.
By using WIN32OLE, you can access OLE server like VBScript.
Here is sample script.
require 'win32ole' excel = WIN32OLE.new('Excel.Application') excel.visible = true workbook = excel.Workbooks.Add(); worksheet = workbook.Worksheets(1); worksheet.Range("A1:D1").value = ["North","South","East","West"]; worksheet.Range("A2:B2").value = [5.2, 10]; worksheet.Range("C2").value = 8; worksheet.Range("D2").value = 20; range = worksheet.Range("A1:D2"); range.select chart = workbook.Charts.Add; workbook.saved = true; excel.ActiveWorkbook.Close(0); excel.Quit();
Unfortunately, Win32OLE doesn’t support the argument passed by reference directly. Instead, Win32OLE provides WIN32OLE::ARGV or WIN32OLE_VARIANT object. If you want to get the result value of argument passed by reference, you can use WIN32OLE::ARGV or WIN32OLE_VARIANT.
oleobj.method(arg1, arg2, refargv3) puts WIN32OLE::ARGV[2] # the value of refargv3 after called oleobj.method
or
refargv3 = WIN32OLE_VARIANT.new(XXX, WIN32OLE::VARIANT::VT_BYREF|WIN32OLE::VARIANT::VT_XXX) oleobj.method(arg1, arg2, refargv3) p refargv3.value # the value of refargv3 after called oleobj.method.
OLEProperty helper class of Property with arguments.
This library provides three different ways to delegate method calls to an object. The easiest to use is SimpleDelegator. Pass an object to the constructor and all methods supported by the object will be delegated. This object can be changed later.
Going a step further, the top level DelegateClass method allows you to easily setup delegation through class inheritance. This is considerably more flexible and thus probably the most common use for this library.
Finally, if you need full control over the delegation scheme, you can inherit from the abstract class Delegator and customize as needed. (If you find yourself needing this control, have a look at Forwardable which is also in the standard library. It may suit your needs better.)
SimpleDelegator’s implementation serves as a nice example of the use of Delegator:
class SimpleDelegator < Delegator def __getobj__ @delegate_sd_obj # return object we are delegating to, required end def __setobj__(obj) @delegate_sd_obj = obj # change delegation object, # a feature we're providing end end
Be advised, RDoc will not detect delegated methods.
A utility class for managing temporary files. When you create a Tempfile object, it will create a temporary file with a unique filename. A Tempfile objects behaves just like a File object, and you can perform all the usual file operations on it: reading data, writing data, changing its permissions, etc. So although this class does not explicitly document all instance methods supported by File, you can in fact call any File instance method on a Tempfile object.
require 'tempfile' file = Tempfile.new('foo') file.path # => A unique filename in the OS's temp directory, # e.g.: "/tmp/foo.24722.0" # This filename contains 'foo' in its basename. file.write("hello world") file.rewind file.read # => "hello world" file.close file.unlink # deletes the temp file
When a Tempfile object is garbage collected, or when the Ruby interpreter exits, its associated temporary file is automatically deleted. This means that’s it’s unnecessary to explicitly delete a Tempfile after use, though it’s good practice to do so: not explicitly deleting unused Tempfiles can potentially leave behind large amounts of tempfiles on the filesystem until they’re garbage collected. The existence of these temp files can make it harder to determine a new Tempfile filename.
Therefore, one should always call unlink or close in an ensure block, like this:
file = Tempfile.new('foo') begin # ...do something with file... ensure file.close file.unlink # deletes the temp file end
On POSIX systems, it’s possible to unlink a file right after creating it, and before closing it. This removes the filesystem entry without closing the file handle, so it ensures that only the processes that already had the file handle open can access the file’s contents. It’s strongly recommended that you do this if you do not want any other processes to be able to read from or write to the Tempfile, and you do not need to know the Tempfile’s filename either.
For example, a practical use case for unlink-after-creation would be this: you need a large byte buffer that’s too large to comfortably fit in RAM, e.g. when you’re writing a web server and you want to buffer the client’s file upload data.
Please refer to unlink for more information and a code example.
Tempfile’s filename picking method is both thread-safe and inter-process-safe: it guarantees that no other threads or processes will pick the same filename.
Tempfile itself however may not be entirely thread-safe. If you access the same Tempfile object from multiple threads then you should protect it with a mutex.
Method objects are created by Object#method, and are associated with a particular object (not just with a class). They may be used to invoke the method within the object, and as a block associated with an iterator. They may also be unbound from one object (creating an UnboundMethod) and bound to another.
class Thing def square(n) n*n end end thing = Thing.new meth = thing.method(:square) meth.call(9) #=> 81 [ 1, 2, 3 ].collect(&meth) #=> [1, 4, 9] [ 1, 2, 3 ].each(&method(:puts)) #=> prints 1, 2, 3 require 'date' %w[2017-03-01 2017-03-02].collect(&Date.method(:parse)) #=> [#<Date: 2017-03-01 ((2457814j,0s,0n),+0s,2299161j)>, #<Date: 2017-03-02 ((2457815j,0s,0n),+0s,2299161j)>]
The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning a value less than 0, returning 0, or returning a value greater than 0, depending on whether the receiver is less than, equal to, or greater than the other object. If the other object is not comparable then the <=> operator should return nil. Comparable uses <=> to implement the conventional comparison operators (<, <=, ==, >=, and >) and the method between?.
class SizeMatters include Comparable attr :str def <=>(other) str.size <=> other.str.size end def initialize(str) @str = str end def inspect @str end end s1 = SizeMatters.new("Z") s2 = SizeMatters.new("YY") s3 = SizeMatters.new("XXX") s4 = SizeMatters.new("WWWW") s5 = SizeMatters.new("VVVVV") s1 < s2 #=> true s4.between?(s1, s3) #=> false s4.between?(s3, s5) #=> true [ s3, s2, s5, s4, s1 ].sort #=> [Z, YY, XXX, WWWW, VVVVV]
The Enumerable mixin provides collection classes with several traversal and searching methods, and with the ability to sort. The class must provide a method each, which yields successive members of the collection. If Enumerable#max, min, or sort is used, the objects in the collection must also implement a meaningful <=> operator, as these methods rely on an ordering between members of the collection.
A libffi wrapper for Ruby.
Fiddle is an extension to translate a foreign function interface (FFI) with ruby.
It wraps libffi, a popular C library which provides a portable interface that allows code written in one language to call code written in another language.
Here we will use Fiddle::Function to wrap floor(3) from libm
require 'fiddle' libm = Fiddle.dlopen('/lib/libm.so.6') floor = Fiddle::Function.new( libm['floor'], [Fiddle::TYPE_DOUBLE], Fiddle::TYPE_DOUBLE ) puts floor.call(3.14159) #=> 3.0