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Kernel#catch

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

Kernel#throw

Transfers control to the end of the active catch block waiting for tag. Raises UncaughtThrowError if there is no catch block for the tag. The optional second parameter supplies a return value for the catch block, which otherwise defaults to nil. For examples, see Kernel::catch.

Enumerable#partition

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.

If no block is given, an enumerator is returned instead.

(1..6).partition { |v| v.even? }  #=> [[2, 4, 6], [1, 3, 5]]

Enumerable#member?

Returns true if any member of enum equals obj. Equality is tested using ==.

IO.constants.include? :SEEK_SET          #=> true
IO.constants.include? :SEEK_NO_FURTHER   #=> false
IO.constants.member? :SEEK_SET          #=> true
IO.constants.member? :SEEK_NO_FURTHER   #=> false

BigMath#atan

Computes the arctangent of decimal to the specified number of digits of precision, numeric.

If decimal is NaN, returns NaN.

BigMath.atan(BigDecimal('-1'), 16).to_s
#=> "-0.785398163397448309615660845819878471907514682065e0"

Etc::passwd

Provides a convenient Ruby iterator which executes a block for each entry in the /etc/passwd file.

The code block is passed an Passwd struct.

See ::getpwent above for details.

Example:

require 'etc'

Etc.passwd {|u|
  puts u.name + " = " + u.gecos
}

JSON#parse

Parse the JSON document source into a Ruby data structure and return it.

opts can have the following keys:

max_nesting: The maximum depth of nesting allowed in the parsed data structures. Disable depth checking with :max_nesting => false. It defaults to 100.
allow_nan: If set to true, allow NaN, Infinity and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to false.
symbolize_names: If set to true, returns symbols for the names (keys) in a JSON object. Otherwise strings are returned. Strings are the default.
create_additions: If set to false, the Parser doesn’t create additions even if a matching class and create_id was found. This option defaults to false.
object_class: Defaults to Hash
array_class: Defaults to Array

JSON#parse!

Parse the JSON document source into a Ruby data structure and return it. The bang version of the parse method defaults to the more dangerous values for the opts hash, so be sure only to parse trusted source documents.

opts can have the following keys:

max_nesting: The maximum depth of nesting allowed in the parsed data structures. Enable depth checking with :max_nesting => anInteger. The parse! methods defaults to not doing max depth checking: This can be dangerous if someone wants to fill up your stack.
allow_nan: If set to true, allow NaN, Infinity, and -Infinity in defiance of RFC 7159 to be parsed by the Parser. This option defaults to true.
create_additions: If set to false, the Parser doesn’t create additions even if a matching class and create_id was found. This option defaults to false.

JSON#generate

Generate a JSON document from the Ruby data structure obj and return it. state is * a JSON::State object,

or a Hash like object (responding to to_hash),
an object convertible into a hash by a to_h method,

that is used as or to configure a State object.

It defaults to a state object, that creates the shortest possible JSON text in one line, checks for circular data structures and doesn’t allow NaN, Infinity, and -Infinity.

A state hash can have the following keys:

indent: a string used to indent levels (default: ”),
space: a string that is put after, a : or , delimiter (default: ”),
space_before: a string that is put before a : pair delimiter (default: ”),
object_nl: a string that is put at the end of a JSON object (default: ”),
array_nl: a string that is put at the end of a JSON array (default: ”),
allow_nan: true if NaN, Infinity, and -Infinity should be generated, otherwise an exception is thrown if these values are encountered. This options defaults to false.
max_nesting: The maximum depth of nesting allowed in the data structures from which JSON is to be generated. Disable depth checking with :max_nesting => false, it defaults to 100.

See also the fast_generate for the fastest creation method with the least amount of sanity checks, and the pretty_generate method for some defaults for pretty output.

Psych::parse

Parse a YAML string in yaml. Returns the Psych::Nodes::Document. filename is used in the exception message if a Psych::SyntaxError is raised.

Raises a Psych::SyntaxError when a YAML syntax error is detected.

Example:

Psych.parse("---\n - a\n - b") # => #<Psych::Nodes::Document:0x00>

begin
  Psych.parse("--- `", filename: "file.txt")
rescue Psych::SyntaxError => ex
  ex.file    # => 'file.txt'
  ex.message # => "(file.txt): found character that cannot start any token"
end

See Psych::Nodes for more information about YAML AST.

Psych::parser

Returns a default parser

PTY::spawn

Spawns the specified command on a newly allocated pty. You can also use the alias ::getpty.

The command’s controlling tty is set to the slave device of the pty and its standard input/output/error is redirected to the slave device.

command and command_line are the full commands to run, given a String. Any additional arguments will be passed to the command.

Return values

In the non-block form this returns an array of size three, [r, w, pid].

In the block form these same values will be yielded to the block:

r: A readable IO that contains the command’s standard output and standard error
w: A writable IO that is the command’s standard input
pid: The process identifier for the command.

Zlib::deflate

Compresses the given string. Valid values of level are Zlib::NO_COMPRESSION, Zlib::BEST_SPEED, Zlib::BEST_COMPRESSION, Zlib::DEFAULT_COMPRESSION, or an integer from 0 to 9.

This method is almost equivalent to the following code:

def deflate(string, level)
  z = Zlib::Deflate.new(level)
  dst = z.deflate(string, Zlib::FINISH)
  z.close
  dst
end

Zlib::inflate

Decompresses string. Raises a Zlib::NeedDict exception if a preset dictionary is needed for decompression.

This method is almost equivalent to the following code:

def inflate(string)
  zstream = Zlib::Inflate.new
  buf = zstream.inflate(string)
  zstream.finish
  zstream.close
  buf
end

GC::enable

Enables garbage collection, returning true if garbage collection was previously disabled.

GC.disable   #=> false
GC.enable    #=> true
GC.enable    #=> false

GC::stat

Returns a Hash containing information about the GC.

The hash includes information about internal statistics about GC such as:

{
    :count=>0,
    :heap_allocated_pages=>24,
    :heap_sorted_length=>24,
    :heap_allocatable_pages=>0,
    :heap_available_slots=>9783,
    :heap_live_slots=>7713,
    :heap_free_slots=>2070,
    :heap_final_slots=>0,
    :heap_marked_slots=>0,
    :heap_eden_pages=>24,
    :heap_tomb_pages=>0,
    :total_allocated_pages=>24,
    :total_freed_pages=>0,
    :total_allocated_objects=>7796,
    :total_freed_objects=>83,
    :malloc_increase_bytes=>2389312,
    :malloc_increase_bytes_limit=>16777216,
    :minor_gc_count=>0,
    :major_gc_count=>0,
    :remembered_wb_unprotected_objects=>0,
    :remembered_wb_unprotected_objects_limit=>0,
    :old_objects=>0,
    :old_objects_limit=>0,
    :oldmalloc_increase_bytes=>2389760,
    :oldmalloc_increase_bytes_limit=>16777216
}

The contents of the hash are implementation specific and may be changed in the future.

This method is only expected to work on C Ruby.

Benchmark#measure

Returns the time used to execute the given block as a Benchmark::Tms object. Takes label option.

require 'benchmark'

n = 1000000

time = Benchmark.measure do
  n.times { a = "1" }
end
puts time

Generates:

0.220000   0.000000   0.220000 (  0.227313)

Benchmark#realtime

Returns the elapsed real time used to execute the given block.

Benchmark::measure