Raised to stop the iteration, in particular by Enumerator#next. It is rescued by Kernel#loop.
loop do puts "Hello" raise StopIteration puts "World" end puts "Done!"
produces:
Hello Done!
Raised by exit to initiate the termination of the script.
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
No longer used by internal code.
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
Outputs a source level execution trace of a Ruby program.
It does this by registering an event handler with Kernel#set_trace_func for processing incoming events. It also provides methods for filtering unwanted trace output (see Tracer.add_filter, Tracer.on, and Tracer.off).
Consider the following Ruby script
class A def square(a) return a*a end end a = A.new a.square(5)
Running the above script using ruby -r tracer example.rb will output the following trace to STDOUT (Note you can also explicitly require 'tracer')
#0:<internal:lib/rubygems/custom_require>:38:Kernel:<: - #0:example.rb:3::-: class A #0:example.rb:3::C: class A #0:example.rb:4::-: def square(a) #0:example.rb:7::E: end #0:example.rb:9::-: a = A.new #0:example.rb:10::-: a.square(5) #0:example.rb:4:A:>: def square(a) #0:example.rb:5:A:-: return a*a #0:example.rb:6:A:<: end | | | | | | | | | ---------------------+ event | | | ------------------------+ class | | --------------------------+ line | ------------------------------------+ filename ---------------------------------------+ thread
Symbol table used for displaying incoming events:
call a C-language routine
return from a C-language routine
call a Ruby method
C
start a class or module definition
E
finish a class or module definition
-
execute code on a new line
raise an exception
return from a Ruby method
by Keiju ISHITSUKA(keiju@ishitsuka.com)
IPAddr provides a set of methods to manipulate an IP address. Both IPv4 and IPv6 are supported.
require 'ipaddr' ipaddr1 = IPAddr.new "3ffe:505:2::1" p ipaddr1 #=> #<IPAddr: IPv6:3ffe:0505:0002:0000:0000:0000:0000:0001/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff> p ipaddr1.to_s #=> "3ffe:505:2::1" ipaddr2 = ipaddr1.mask(48) #=> #<IPAddr: IPv6:3ffe:0505:0002:0000:0000:0000:0000:0000/ffff:ffff:ffff:0000:0000:0000:0000:0000> p ipaddr2.to_s #=> "3ffe:505:2::" ipaddr3 = IPAddr.new "192.168.2.0/24" p ipaddr3 #=> #<IPAddr: IPv4:192.168.2.0/255.255.255.0>
This class implements a pretty printing algorithm. It finds line breaks and nice indentations for grouped structure.
By default, the class assumes that primitive elements are strings and each byte in the strings have single column in width. But it can be used for other situations by giving suitable arguments for some methods:
newline object and space generation block for PrettyPrint.new
optional width argument for PrettyPrint#text
There are several candidate uses:
text formatting using proportional fonts
multibyte characters which has columns different to number of bytes
non-string formatting
Box based formatting?
Other (better) model/algorithm?
Report any bugs at bugs.ruby-lang.org
Christian Lindig, Strictly Pretty, March 2000, www.st.cs.uni-sb.de/~lindig/papers/#pretty
Philip Wadler, A prettier printer, March 1998, homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier
Tanaka Akira <akr@fsij.org>
The set of all prime numbers.
Prime.each(100) do |prime| p prime #=> 2, 3, 5, 7, 11, ...., 97 end
Prime is Enumerable:
Prime.first 5 # => [2, 3, 5, 7, 11]
For convenience, each instance method of Prime.instance can be accessed as a class method of Prime.
e.g.
Prime.instance.prime?(2) #=> true Prime.prime?(2) #=> true
A “generator” provides an implementation of enumerating pseudo-prime numbers and it remembers the position of enumeration and upper bound. Furthermore, it is an external iterator of prime enumeration which is compatible with an Enumerator.
Prime::PseudoPrimeGenerator is the base class for generators. There are few implementations of generator.
Prime::EratosthenesGenerator
Uses eratosthenes’ sieve.
Prime::TrialDivisionGenerator
Uses the trial division method.
Prime::Generator23
Generates all positive integers which are not divisible by either 2 or 3. This sequence is very bad as a pseudo-prime sequence. But this is faster and uses much less memory than the other generators. So, it is suitable for factorizing an integer which is not large but has many prime factors. e.g. for Prime#prime? .
PStore implements a file based persistence mechanism based on a Hash. User code can store hierarchies of Ruby objects (values) into the data store file by name (keys). An object hierarchy may be just a single object. User code may later read values back from the data store or even update data, as needed.
The transactional behavior ensures that any changes succeed or fail together. This can be used to ensure that the data store is not left in a transitory state, where some values were updated but others were not.
Behind the scenes, Ruby objects are stored to the data store file with Marshal. That carries the usual limitations. Proc objects cannot be marshalled, for example.
require "pstore" # a mock wiki object... class WikiPage def initialize( page_name, author, contents ) @page_name = page_name @revisions = Array.new add_revision(author, contents) end attr_reader :page_name def add_revision( author, contents ) @revisions << { :created => Time.now, :author => author, :contents => contents } end def wiki_page_references [@page_name] + @revisions.last[:contents].scan(/\b(?:[A-Z]+[a-z]+){2,}/) end # ... end # create a new page... home_page = WikiPage.new( "HomePage", "James Edward Gray II", "A page about the JoysOfDocumentation..." ) # then we want to update page data and the index together, or not at all... wiki = PStore.new("wiki_pages.pstore") wiki.transaction do # begin transaction; do all of this or none of it # store page... wiki[home_page.page_name] = home_page # ensure that an index has been created... wiki[:wiki_index] ||= Array.new # update wiki index... wiki[:wiki_index].push(*home_page.wiki_page_references) end # commit changes to wiki data store file ### Some time later... ### # read wiki data... wiki.transaction(true) do # begin read-only transaction, no changes allowed wiki.roots.each do |data_root_name| p data_root_name p wiki[data_root_name] end end
By default, file integrity is only ensured as long as the operating system (and the underlying hardware) doesn’t raise any unexpected I/O errors. If an I/O error occurs while PStore is writing to its file, then the file will become corrupted.
You can prevent this by setting pstore.ultra_safe = true. However, this results in a minor performance loss, and only works on platforms that support atomic file renames. Please consult the documentation for ultra_safe for details.
Needless to say, if you’re storing valuable data with PStore, then you should backup the PStore files from time to time.
The global value true is the only instance of class TrueClass and represents a logically true value in boolean expressions. The class provides operators allowing true to be used in logical expressions.
ConditionVariable objects augment class Mutex. Using condition variables, it is possible to suspend while in the middle of a critical section until a resource becomes available.
Example:
mutex = Mutex.new resource = ConditionVariable.new a = Thread.new { mutex.synchronize { # Thread 'a' now needs the resource resource.wait(mutex) # 'a' can now have the resource } } b = Thread.new { mutex.synchronize { # Thread 'b' has finished using the resource resource.signal } }
Document-class: TracePoint
A class that provides the functionality of Kernel#set_trace_func in a nice Object-Oriented API.
We can use TracePoint to gather information specifically for exceptions:
trace = TracePoint.new(:raise) do |tp| p [tp.lineno, tp.event, tp.raised_exception] end #=> #<TracePoint:disabled> trace.enable #=> false 0 / 0 #=> [5, :raise, #<ZeroDivisionError: divided by 0>]
If you don’t specify the type of events you want to listen for, TracePoint will include all available events.
Note do not depend on current event set, as this list is subject to change. Instead, it is recommended you specify the type of events you want to use.
To filter what is traced, you can pass any of the following as events:
:line
execute code on a new line
:class
start a class or module definition
:end
finish a class or module definition
:call
call a Ruby method
:return
return from a Ruby method
:c_call
call a C-language routine
:c_return
return from a C-language routine
:raise
raise an exception
:b_call
event hook at block entry
:b_return
event hook at block ending
:thread_begin
event hook at thread beginning
:thread_end
event hook at thread ending
:fiber_switch
event hook at fiber switch
:script_compiled
new Ruby code compiled (with eval, load or require)
This module provides a framework for message digest libraries.
You may want to look at OpenSSL::Digest as it supports more algorithms.
A cryptographic hash function is a procedure that takes data and returns a fixed bit string: the hash value, also known as digest. Hash functions are also called one-way functions, it is easy to compute a digest from a message, but it is infeasible to generate a message from a digest.
require 'digest' # Compute a complete digest Digest::SHA256.digest 'message' #=> "\xABS\n\x13\xE4Y..." sha256 = Digest::SHA256.new sha256.digest 'message' #=> "\xABS\n\x13\xE4Y..." # Other encoding formats Digest::SHA256.hexdigest 'message' #=> "ab530a13e459..." Digest::SHA256.base64digest 'message' #=> "q1MKE+RZFJgr..." # Compute digest by chunks md5 = Digest::MD5.new md5.update 'message1' md5 << 'message2' # << is an alias for update md5.hexdigest #=> "94af09c09bb9..." # Compute digest for a file sha256 = Digest::SHA256.file 'testfile' sha256.hexdigest
Additionally digests can be encoded in “bubble babble” format as a sequence of consonants and vowels which is more recognizable and comparable than a hexadecimal digest.
require 'digest/bubblebabble' Digest::SHA256.bubblebabble 'message' #=> "xopoh-fedac-fenyh-..."
See the bubble babble specification at web.mit.edu/kenta/www/one/bubblebabble/spec/jrtrjwzi/draft-huima-01.txt.
Digest algorithms Different digest algorithms (or hash functions) are available:
MD5
See RFC 1321 The MD5 Message-Digest Algorithm
As Digest::RMD160. See homes.esat.kuleuven.be/~bosselae/ripemd160.html.
SHA1
See FIPS 180 Secure Hash Standard.
See FIPS 180 Secure Hash Standard which defines the following algorithms:
SHA512
SHA384
SHA256
The latest versions of the FIPS publications can be found here: csrc.nist.gov/publications/PubsFIPS.html.
FileTest implements file test operations similar to those used in File::Stat. It exists as a standalone module, and its methods are also insinuated into the File class. (Note that this is not done by inclusion: the interpreter cheats).
URI is a module providing classes to handle Uniform Resource Identifiers (RFC2396).
Uniform way of handling URIs.
Flexibility to introduce custom URI schemes.
Flexibility to have an alternate URI::Parser (or just different patterns and regexp’s).
require 'uri' uri = URI("http://foo.com/posts?id=30&limit=5#time=1305298413") #=> #<URI::HTTP http://foo.com/posts?id=30&limit=5#time=1305298413> uri.scheme #=> "http" uri.host #=> "foo.com" uri.path #=> "/posts" uri.query #=> "id=30&limit=5" uri.fragment #=> "time=1305298413" uri.to_s #=> "http://foo.com/posts?id=30&limit=5#time=1305298413"
module URI class RSYNC < Generic DEFAULT_PORT = 873 end @@schemes['RSYNC'] = RSYNC end #=> URI::RSYNC URI.scheme_list #=> {"FILE"=>URI::File, "FTP"=>URI::FTP, "HTTP"=>URI::HTTP, # "HTTPS"=>URI::HTTPS, "LDAP"=>URI::LDAP, "LDAPS"=>URI::LDAPS, # "MAILTO"=>URI::MailTo, "RSYNC"=>URI::RSYNC} uri = URI("rsync://rsync.foo.com") #=> #<URI::RSYNC rsync://rsync.foo.com>
A good place to view an RFC spec is www.ietf.org/rfc.html.
Here is a list of all related RFC’s:
Class tree URI::Generic (in uri/generic.rb)
URI::File - (in uri/file.rb)
URI::FTP - (in uri/ftp.rb)
URI::HTTP - (in uri/http.rb)
URI::HTTPS - (in uri/https.rb)
URI::LDAP - (in uri/ldap.rb)
URI::LDAPS - (in uri/ldaps.rb)
URI::MailTo - (in uri/mailto.rb)
URI::Parser - (in uri/common.rb)
URI::REGEXP - (in uri/common.rb)
URI::REGEXP::PATTERN - (in uri/common.rb)
URI::Util - (in uri/common.rb)
URI::Escape - (in uri/common.rb)
URI::Error - (in uri/common.rb)
URI::InvalidURIError - (in uri/common.rb)
URI::InvalidComponentError - (in uri/common.rb)
URI::BadURIError - (in uri/common.rb)
Akira Yamada <akira@ruby-lang.org>
Akira Yamada <akira@ruby-lang.org> Dmitry V. Sabanin <sdmitry@lrn.ru> Vincent Batts <vbatts@hashbangbash.com>
Copyright © 2001 akira yamada <akira@ruby-lang.org> You can redistribute it and/or modify it under the same term as Ruby.
$Id$