Results for: "Data"

Verifies that data matches the signature created by public_key and the digest algorithm.

Returns the concatenated string from strings.

Load extra data embed into binary format String object.

Subclass of Zlib::Error when zlib returns a Z_DATA_ERROR.

Usually if a stream was prematurely freed.

MatchData encapsulates the result of matching a Regexp against string. It is returned by Regexp#match and String#match, and also stored in a global variable returned by Regexp.last_match.

Usage:

url = 'https://docs.ruby-lang.org/en/2.5.0/MatchData.html'
m = url.match(/(\d\.?)+/)   # => #<MatchData "2.5.0" 1:"0">
m.string                    # => "https://docs.ruby-lang.org/en/2.5.0/MatchData.html"
m.regexp                    # => /(\d\.?)+/
# entire matched substring:
m[0]                        # => "2.5.0"

# Working with unnamed captures
m = url.match(%r{([^/]+)/([^/]+)\.html$})
m.captures                  # => ["2.5.0", "MatchData"]
m[1]                        # => "2.5.0"
m.values_at(1, 2)           # => ["2.5.0", "MatchData"]

# Working with named captures
m = url.match(%r{(?<version>[^/]+)/(?<module>[^/]+)\.html$})
m.captures                  # => ["2.5.0", "MatchData"]
m.named_captures            # => {"version"=>"2.5.0", "module"=>"MatchData"}
m[:version]                 # => "2.5.0"
m.values_at(:version, :module)
                            # => ["2.5.0", "MatchData"]
# Numerical indexes are working, too
m[1]                        # => "2.5.0"
m.values_at(1, 2)           # => ["2.5.0", "MatchData"]

Global variables equivalence

Parts of last MatchData (returned by Regexp.last_match) are also aliased as global variables:

• $~ is Regexp.last_match;

• $& is Regexp.last_match[ 0 ];

• $1, $2, and so on are Regexp.last_match[ i ] (captures by number);

• $` is Regexp.last_match.pre_match;

• $' is Regexp.last_match.post_match;

• $+ is Regexp.last_match[ -1 ] (the last capture).

See also “Special global variables” section in Regexp documentation.

fatal is an Exception that is raised when Ruby has encountered a fatal error and must exit.

The most standard error types are subclasses of StandardError. A rescue clause without an explicit Exception class will rescue all StandardErrors (and only those).

def foo
  raise "Oups"
end
foo rescue "Hello"   #=> "Hello"

On the other hand:

require 'does/not/exist' rescue "Hi"

raises the exception:

LoadError: no such file to load -- does/not/exist

Class Date provides methods for storing and manipulating calendar dates.

Consider using class Time instead of class Date if:

• You need both dates and times; Date handles only dates.

• You need only Gregorian dates (and not Julian dates); see Julian and Gregorian Calendars.

A Date object, once created, is immutable, and cannot be modified.

Creating a Date

You can create a date for the current date, using Date.today:

Date.today # => #<Date: 1999-12-31>

You can create a specific date from various combinations of arguments:

• Date.new takes integer year, month, and day-of-month:

  Date.new(1999, 12, 31) # => #<Date: 1999-12-31>
  

• Date.ordinal takes integer year and day-of-year:

  Date.ordinal(1999, 365) # => #<Date: 1999-12-31>
  

• Date.jd takes integer Julian day:

  Date.jd(2451544) # => #<Date: 1999-12-31>
  

• Date.commercial takes integer commercial data (year, week, day-of-week):

  Date.commercial(1999, 52, 5) # => #<Date: 1999-12-31>
  

• Date.parse takes a string, which it parses heuristically:

  Date.parse('1999-12-31')    # => #<Date: 1999-12-31>
  Date.parse('31-12-1999')    # => #<Date: 1999-12-31>
  Date.parse('1999-365')      # => #<Date: 1999-12-31>
  Date.parse('1999-W52-5')    # => #<Date: 1999-12-31>
  

• Date.strptime takes a date string and a format string, then parses the date string according to the format string:

  Date.strptime('1999-12-31', '%Y-%m-%d')  # => #<Date: 1999-12-31>
  Date.strptime('31-12-1999', '%d-%m-%Y')  # => #<Date: 1999-12-31>
  Date.strptime('1999-365', '%Y-%j')       # => #<Date: 1999-12-31>
  Date.strptime('1999-W52-5', '%G-W%V-%u') # => #<Date: 1999-12-31>
  Date.strptime('1999 52 5', '%Y %U %w')   # => #<Date: 1999-12-31>
  Date.strptime('1999 52 5', '%Y %W %u')   # => #<Date: 1999-12-31>
  Date.strptime('fri31dec99', '%a%d%b%y')  # => #<Date: 1999-12-31>
  

See also the specialized methods in “Specialized Format Strings” in Formats for Dates and Times

Argument limit

Certain singleton methods in Date that parse string arguments also take optional keyword argument limit, which can limit the length of the string argument.

When limit is:

• Non-negative: raises ArgumentError if the string length is greater than limit.

• Other numeric or nil: ignores limit.

• Other non-numeric: raises TypeError.

DateTime

A subclass of Date that easily handles date, hour, minute, second, and offset.

DateTime class is considered deprecated. Use Time class.

DateTime does not consider any leap seconds, does not track any summer time rules.

A DateTime object is created with DateTime::new, DateTime::jd, DateTime::ordinal, DateTime::commercial, DateTime::parse, DateTime::strptime, DateTime::now, Time#to_datetime, etc.

require 'date'

DateTime.new(2001,2,3,4,5,6)
                    #=> #<DateTime: 2001-02-03T04:05:06+00:00 ...>

The last element of day, hour, minute, or second can be a fractional number. The fractional number’s precision is assumed at most nanosecond.

DateTime.new(2001,2,3.5)
                    #=> #<DateTime: 2001-02-03T12:00:00+00:00 ...>

An optional argument, the offset, indicates the difference between the local time and UTC. For example, Rational(3,24) represents ahead of 3 hours of UTC, Rational(-5,24) represents behind of 5 hours of UTC. The offset should be -1 to +1, and its precision is assumed at most second. The default value is zero (equals to UTC).

DateTime.new(2001,2,3,4,5,6,Rational(3,24))
                    #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>

The offset also accepts string form:

DateTime.new(2001,2,3,4,5,6,'+03:00')
                    #=> #<DateTime: 2001-02-03T04:05:06+03:00 ...>

An optional argument, the day of calendar reform (start), denotes a Julian day number, which should be 2298874 to 2426355 or negative/positive infinity. The default value is Date::ITALY (2299161=1582-10-15).

A DateTime object has various methods. See each reference.

d = DateTime.parse('3rd Feb 2001 04:05:06+03:30')
                    #=> #<DateTime: 2001-02-03T04:05:06+03:30 ...>
d.hour              #=> 4
d.min               #=> 5
d.sec               #=> 6
d.offset            #=> (7/48)
d.zone              #=> "+03:30"
d += Rational('1.5')
                    #=> #<DateTime: 2001-02-04%16:05:06+03:30 ...>
d = d.new_offset('+09:00')
                    #=> #<DateTime: 2001-02-04%21:35:06+09:00 ...>
d.strftime('%I:%M:%S %p')
                    #=> "09:35:06 PM"
d > DateTime.new(1999)
                    #=> true

When should you use DateTime and when should you use Time?

It’s a common misconception that William Shakespeare and Miguel de Cervantes died on the same day in history - so much so that UNESCO named April 23 as World Book Day because of this fact. However, because England hadn’t yet adopted the Gregorian Calendar Reform (and wouldn’t until 1752) their deaths are actually 10 days apart. Since Ruby’s Time class implements a proleptic Gregorian calendar and has no concept of calendar reform there’s no way to express this with Time objects. This is where DateTime steps in:

shakespeare = DateTime.iso8601('1616-04-23', Date::ENGLAND)
 #=> Tue, 23 Apr 1616 00:00:00 +0000
cervantes = DateTime.iso8601('1616-04-23', Date::ITALY)
 #=> Sat, 23 Apr 1616 00:00:00 +0000

Already you can see something is weird - the days of the week are different. Taking this further:

cervantes == shakespeare
 #=> false
(shakespeare - cervantes).to_i
 #=> 10

This shows that in fact they died 10 days apart (in reality 11 days since Cervantes died a day earlier but was buried on the 23rd). We can see the actual date of Shakespeare’s death by using the gregorian method to convert it:

shakespeare.gregorian
 #=> Tue, 03 May 1616 00:00:00 +0000

So there’s an argument that all the celebrations that take place on the 23rd April in Stratford-upon-Avon are actually the wrong date since England is now using the Gregorian calendar. You can see why when we transition across the reform date boundary:

# start off with the anniversary of Shakespeare's birth in 1751
shakespeare = DateTime.iso8601('1751-04-23', Date::ENGLAND)
 #=> Tue, 23 Apr 1751 00:00:00 +0000

# add 366 days since 1752 is a leap year and April 23 is after February 29
shakespeare + 366
 #=> Thu, 23 Apr 1752 00:00:00 +0000

# add another 365 days to take us to the anniversary in 1753
shakespeare + 366 + 365
 #=> Fri, 04 May 1753 00:00:00 +0000

As you can see, if we’re accurately tracking the number of solar years since Shakespeare’s birthday then the correct anniversary date would be the 4th May and not the 23rd April.

So when should you use DateTime in Ruby and when should you use Time? Almost certainly you’ll want to use Time since your app is probably dealing with current dates and times. However, if you need to deal with dates and times in a historical context you’ll want to use DateTime to avoid making the same mistakes as UNESCO. If you also have to deal with timezones then best of luck - just bear in mind that you’ll probably be dealing with local solar times, since it wasn’t until the 19th century that the introduction of the railways necessitated the need for Standard Time and eventually timezones.

Socket::AncillaryData represents the ancillary data (control information) used by sendmsg and recvmsg system call. It contains socket family, control message (cmsg) level, cmsg type and cmsg data.

Response class for Non-Authoritative Information responses (status code 203).

The Non-Authoritative Information response indicates that the server is a transforming proxy (such as a Web accelerator) that received a 200 OK response from its origin, and is returning a modified version of the origin’s response.

References:

• Mozilla.

• RFC 9110.

• Wikipedia.

Mixin methods for install and update options for Gem::Commands

A Float object represents a sometimes-inexact real number using the native architecture’s double-precision floating point representation.

Floating point has a different arithmetic and is an inexact number. So you should know its esoteric system. See following:

• docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

• github.com/rdp/ruby_tutorials_core/wiki/Ruby-Talk-FAQ#-why-are-rubys-floats-imprecise

• en.wikipedia.org/wiki/Floating_point#Accuracy_problems

You can create a Float object explicitly with:

• A floating-point literal.

You can convert certain objects to Floats with:

• Method Float.

What’s Here

First, what’s elsewhere. Class Float:

• Inherits from class Numeric and class Object.

• Includes module Comparable.

Here, class Float provides methods for:

• Querying

• Comparing

• Converting

Querying

• finite?: Returns whether self is finite.

• hash: Returns the integer hash code for self.

• infinite?: Returns whether self is infinite.

• nan?: Returns whether self is a NaN (not-a-number).

Comparing

• <: Returns whether self is less than the given value.

• <=: Returns whether self is less than or equal to the given value.

• <=>: Returns a number indicating whether self is less than, equal to, or greater than the given value.

• == (aliased as === and eql?): Returns whether self is equal to the given value.

• >: Returns whether self is greater than the given value.

• >=: Returns whether self is greater than or equal to the given value.

Converting

• % (aliased as modulo): Returns self modulo the given value.

• *: Returns the product of self and the given value.

• **: Returns the value of self raised to the power of the given value.

• +: Returns the sum of self and the given value.

• -: Returns the difference of self and the given value.

• /: Returns the quotient of self and the given value.

• ceil: Returns the smallest number greater than or equal to self.

• coerce: Returns a 2-element array containing the given value converted to a Float and self

• divmod: Returns a 2-element array containing the quotient and remainder results of dividing self by the given value.

• fdiv: Returns the Float result of dividing self by the given value.

• floor: Returns the greatest number smaller than or equal to self.

• next_float: Returns the next-larger representable Float.

• prev_float: Returns the next-smaller representable Float.

• quo: Returns the quotient from dividing self by the given value.

• round: Returns self rounded to the nearest value, to a given precision.

• to_i (aliased as to_int): Returns self truncated to an Integer.

• to_s (aliased as inspect): Returns a string containing the place-value representation of self in the given radix.

• truncate: Returns self truncated to a given precision.

Continuation objects are generated by Kernel#callcc, after having +require+d continuation. They hold a return address and execution context, allowing a nonlocal return to the end of the callcc block from anywhere within a program. Continuations are somewhat analogous to a structured version of C’s setjmp/longjmp (although they contain more state, so you might consider them closer to threads).

For instance:

require "continuation"
arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
callcc{|cc| $cc = cc}
puts(message = arr.shift)
$cc.call unless message =~ /Max/

produces:

Freddie
Herbie
Ron
Max

Also you can call callcc in other methods:

require "continuation"

def g
  arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
  cc = callcc { |cc| cc }
  puts arr.shift
  return cc, arr.size
end

def f
  c, size = g
  c.call(c) if size > 1
end

f

This (somewhat contrived) example allows the inner loop to abandon processing early:

require "continuation"
callcc {|cont|
  for i in 0..4
    print "#{i}: "
    for j in i*5...(i+1)*5
      cont.call() if j == 17
      printf "%3d", j
    end
  end
}
puts

produces:

0:   0  1  2  3  4
1:   5  6  7  8  9
2:  10 11 12 13 14
3:  15 16