Yields each environment variable name and value.
If no block is given an Enumerator is returned.
This method is intended as the primary interface for reading CSV files. You pass a path and any options you wish to set for the read. Each row of file will be passed to the provided block in turn.
The options parameter can be anything CSV::new() understands. This method also understands an additional :encoding parameter that you can use to specify the Encoding of the data in the file to be read. You must provide this unless your data is in Encoding::default_external(). CSV will use this to determine how to parse the data. You may provide a second Encoding to have the data transcoded as it is read. For example, encoding: "UTF-32BE:UTF-8" would read UTF-32BE data from the file but transcode it to UTF-8 before CSV parses it.
Yields each row of the data source in turn.
Support for Enumerable.
The data source must be open for reading.
Iterator version of ‘get’.
The block is called repeatedly with two arguments: The first is the option name. The second is the argument which followed it (if any). Example: (‘–opt’, ‘value’)
The option name is always converted to the first (preferred) name given in the original options to GetoptLong.new.
Yields all elements of the matrix, starting with those of the first row, or returns an Enumerator if no block given. Elements can be restricted by passing an argument:
:all (default): yields all elements
:diagonal: yields only elements on the diagonal
:off_diagonal: yields all elements except on the diagonal
:lower: yields only elements on or below the diagonal
:strict_lower: yields only elements below the diagonal
:strict_upper: yields only elements above the diagonal
:upper: yields only elements on or above the diagonal
Matrix[ [1,2], [3,4] ].each { |e| puts e }
# => prints the numbers 1 to 4
Matrix[ [1,2], [3,4] ].each(:strict_lower).to_a # => [3]
Returns true if this is a symmetric matrix. Raises an error if matrix is not square.
Returns the Eigensystem of the matrix; see EigenvalueDecomposition.
m = Matrix[[1, 2], [3, 4]] v, d, v_inv = m.eigensystem d.diagonal? # => true v.inv == v_inv # => true (v * d * v_inv).round(5) == m # => true
Iterate over the elements of this vector
Iterate over the elements of this vector and v in conjunction.
Searches key in @stack for id hash and returns or yields the result.
Searches key in @stack for id hash and returns or yields the result.
Iterates the given block over all prime numbers.
uboundOptional. An arbitrary positive number. The upper bound of enumeration. The method enumerates prime numbers infinitely if ubound is nil.
generatorOptional. An implementation of pseudo-prime generator.
An evaluated value of the given block at the last time. Or an enumerator which is compatible to an Enumerator if no block given.
Calls block once for each prime number, passing the prime as a parameter.
uboundUpper bound of prime numbers. The iterator stops after it yields all prime numbers p <= ubound.
This method is just like PStore#[], save that you may also provide a default value for the object. In the event the specified name is not found in the data store, your default will be returned instead. If you do not specify a default, PStore::Error will be raised if the object is not found.
WARNING: This method is only valid in a PStore#transaction. It will raise PStore::Error if called at any other time.
Returns a string containing the character represented by the int‘s value according to encoding.
65.chr #=> "A" 230.chr #=> "\346" 255.chr(Encoding::UTF_8) #=> "\303\277"
Calls the given block once for each element in the set, passing the element as parameter. Returns an enumerator if no block is given.
Creates a Shell object which current directory is set to path.
If a block is given, it restores the current directory when the block ends.
If called as iterator, it restores the current directory when the block ends.
Calls the operating system function identified by num and returns the result of the function or raises SystemCallError if it failed.
Arguments for the function can follow num. They must be either String objects or Integer objects. A String object is passed as a pointer to the byte sequence. An Integer object is passed as an integer whose bit size is same as a pointer. Up to nine parameters may be passed (14 on the Atari-ST).
The function identified by num is system dependent. On some Unix systems, the numbers may be obtained from a header file called syscall.h.
syscall 4, 1, "hello\n", 6 # '4' is write(2) on our box
produces:
hello
Calling syscall on a platform which does not have any way to an arbitrary system function just fails with NotImplementedError.
Note: syscall is essentially unsafe and unportable. Feel free to shoot your foot. The DL (Fiddle) library is preferred for safer and a bit more portable programming.
Executes command… in a subshell. command… is one of following forms.
commandline : command line string which is passed to the standard shell cmdname, arg1, ... : command name and one or more arguments (no shell) [cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
system returns true if the command gives zero exit status, false for non zero exit status. Returns nil if command execution fails. An error status is available in $?. The arguments are processed in the same way as for Kernel.spawn.
The hash arguments, env and options, are same as exec and spawn. See Kernel.spawn for details.
system("echo *") system("echo", "*")
produces:
config.h main.rb *
See Kernel.exec for the standard shell.
Equivalent to ($_.dup).chop!, except nil is never returned. See String#chop!. Available only when -p/-n command line option specified.
Equivalent to $_ = $_.chomp(string). See String#chomp. Available only when -p/-n command line option specified.
catch executes its block. If throw is not called, the block executes normally, and catch returns the value of the last expression evaluated.
catch(1) { 123 } # => 123
If throw(tag2, val) is called, Ruby searches up its stack for a catch block whose tag has the same object_id as tag2. When found, the block stops executing and returns val (or nil if no second argument was given to throw).
catch(1) { throw(1, 456) } # => 456 catch(1) { throw(1) } # => nil
When tag is passed as the first argument, catch yields it as the parameter of the block.
catch(1) {|x| x + 2 } # => 3
When no tag is given, catch yields a new unique object (as from Object.new) as the block parameter. This object can then be used as the argument to throw, and will match the correct catch block.
catch do |obj_A| catch do |obj_B| throw(obj_B, 123) puts "This puts is not reached" end puts "This puts is displayed" 456 end # => 456 catch do |obj_A| catch do |obj_B| throw(obj_A, 123) puts "This puts is still not reached" end puts "Now this puts is also not reached" 456 end # => 123
Calls block for each element of enum repeatedly n times or forever if none or nil is given. If a non-positive number is given or the collection is empty, does nothing. Returns nil if the loop has finished without getting interrupted.
Enumerable#cycle saves elements in an internal array so changes to enum after the first pass have no effect.
If no block is given, an enumerator is returned instead.
a = ["a", "b", "c"] a.cycle { |x| puts x } # print, a, b, c, a, b, c,.. forever. a.cycle(2) { |x| puts x } # print, a, b, c, a, b, c.
Enumerates over the items, chunking them together based on the return value of the block.
Consecutive elements which return the same block value are chunked together.
For example, consecutive even numbers and odd numbers can be chunked as follows.
[3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5].chunk { |n| n.even? }.each { |even, ary| p [even, ary] } #=> [false, [3, 1]] # [true, [4]] # [false, [1, 5, 9]] # [true, [2, 6]] # [false, [5, 3, 5]]
This method is especially useful for sorted series of elements. The following example counts words for each initial letter.
open("/usr/share/dict/words", "r:iso-8859-1") { |f| f.chunk { |line| line.ord }.each { |ch, lines| p [ch.chr, lines.length] } } #=> ["\n", 1] # ["A", 1327] # ["B", 1372] # ["C", 1507] # ["D", 791] # ...
The following key values have special meaning:
nil and :_separator specifies that the elements should be dropped.
:_alone specifies that the element should be chunked by itself.
Any other symbols that begin with an underscore will raise an error:
items.chunk { |item| :_underscore } #=> RuntimeError: symbols beginning with an underscore are reserved
nil and :_separator can be used to ignore some elements.
For example, the sequence of hyphens in svn log can be eliminated as follows:
sep = "-"*72 + "\n" IO.popen("svn log README") { |f| f.chunk { |line| line != sep || nil }.each { |_, lines| pp lines } } #=> ["r20018 | knu | 2008-10-29 13:20:42 +0900 (Wed, 29 Oct 2008) | 2 lines\n", # "\n", # "* README, README.ja: Update the portability section.\n", # "\n"] # ["r16725 | knu | 2008-05-31 23:34:23 +0900 (Sat, 31 May 2008) | 2 lines\n", # "\n", # "* README, README.ja: Add a note about default C flags.\n", # "\n"] # ...
Paragraphs separated by empty lines can be parsed as follows:
File.foreach("README").chunk { |line| /\A\s*\z/ !~ line || nil }.each { |_, lines| pp lines }
:_alone can be used to force items into their own chunk. For example, you can put lines that contain a URL by themselves, and chunk the rest of the lines together, like this:
pattern = /http/ open(filename) { |f| f.chunk { |line| line =~ pattern ? :_alone : true }.each { |key, lines| pp lines } }
Returns system configuration directory.
This is typically “/etc”, but is modified by the prefix used when Ruby was compiled. For example, if Ruby is built and installed in /usr/local, returns “/usr/local/etc”.
Returns system temporary directory; typically “/tmp”.