Converts block to a Proc object (and therefore binds it at the point of call) and registers it for execution when the program exits. If multiple handlers are registered, they are executed in reverse order of registration.
def do_at_exit(str1) at_exit { print str1 } end at_exit { puts "cruel world" } do_at_exit("goodbye ") exit
produces:
goodbye cruel world
Ruby tries to load the library named string relative to the requiring file’s path. If the file’s path cannot be determined a LoadError is raised. If a file is loaded true is returned and false otherwise.
Returns the current execution stack—an array containing backtrace location objects.
See Thread::Backtrace::Location for more information.
The optional start parameter determines the number of initial stack entries to omit from the top of the stack.
A second optional length parameter can be used to limit how many entries are returned from the stack.
Returns nil if start is greater than the size of current execution stack.
Optionally you can pass a range, which will return an array containing the entries within the specified range.
Returns a new array containing the truthy results (everything except false or nil) of running the block for every element in enum.
If no block is given, an Enumerator is returned instead.
(1..10).filter_map { |i| i * 2 if i.even? } #=> [4, 8, 12, 16, 20]
Returns a new array with the concatenated results of running block once for every element in enum.
If no block is given, an enumerator is returned instead.
[1, 2, 3, 4].flat_map { |e| [e, -e] } #=> [1, -1, 2, -2, 3, -3, 4, -4] [[1, 2], [3, 4]].flat_map { |e| e + [100] } #=> [1, 2, 100, 3, 4, 100]
Returns the object in enum that gives the maximum value from the given block.
If no block is given, an enumerator is returned instead.
a = %w(albatross dog horse) a.max_by { |x| x.length } #=> "albatross"
If the n argument is given, maximum n elements are returned as an array. These n elements are sorted by the value from the given block, in descending order.
a = %w[albatross dog horse] a.max_by(2) {|x| x.length } #=> ["albatross", "horse"]
enum.max_by(n) can be used to implement weighted random sampling. Following example implements and use Enumerable#wsample.
module Enumerable # weighted random sampling. # # Pavlos S. Efraimidis, Paul G. Spirakis # Weighted random sampling with a reservoir # Information Processing Letters # Volume 97, Issue 5 (16 March 2006) def wsample(n) self.max_by(n) {|v| rand ** (1.0/yield(v)) } end end e = (-20..20).to_a*10000 a = e.wsample(20000) {|x| Math.exp(-(x/5.0)**2) # normal distribution } # a is 20000 samples from e. p a.length #=> 20000 h = a.group_by {|x| x } -10.upto(10) {|x| puts "*" * (h[x].length/30.0).to_i if h[x] } #=> * # *** # ****** # *********** # ****************** # ***************************** # ***************************************** # **************************************************** # *************************************************************** # ******************************************************************** # *********************************************************************** # *********************************************************************** # ************************************************************** # **************************************************** # *************************************** # *************************** # ****************** # *********** # ******* # *** # *
Builds a temporary array and traverses that array in reverse order.
If no block is given, an enumerator is returned instead.
(1..3).reverse_each { |v| p v }
produces:
3 2 1
Calls block once for each element in self, passing that element as a parameter, converting multiple values from yield to an array.
If no block is given, an enumerator is returned instead.
class Foo include Enumerable def each yield 1 yield 1, 2 yield end end Foo.new.each_entry{ |o| p o }
produces:
1 [1, 2] nil
Iterates the given block for each slice of <n> elements. If no block is given, returns an enumerator.
(1..10).each_slice(3) { |a| p a } # outputs below [1, 2, 3] [4, 5, 6] [7, 8, 9] [10]
Iterates the given block for each array of consecutive <n> elements. If no block is given, returns an enumerator.
e.g.:
(1..10).each_cons(3) { |a| p a } # outputs below [1, 2, 3] [2, 3, 4] [3, 4, 5] [4, 5, 6] [5, 6, 7] [6, 7, 8] [7, 8, 9] [8, 9, 10]
Creates an enumerator for each chunked elements. The beginnings of chunks are defined by the block.
This method splits each chunk using adjacent elements, elt_before and elt_after, in the receiver enumerator. This method split chunks between elt_before and elt_after where the block returns false.
The block is called the length of the receiver enumerator minus one.
The result enumerator yields the chunked elements as an array. So each method can be called as follows:
enum.chunk_while { |elt_before, elt_after| bool }.each { |ary| ... }
Other methods of the Enumerator class and Enumerable module, such as to_a, map, etc., are also usable.
For example, one-by-one increasing subsequence can be chunked as follows:
a = [1,2,4,9,10,11,12,15,16,19,20,21] b = a.chunk_while {|i, j| i+1 == j } p b.to_a #=> [[1, 2], [4], [9, 10, 11, 12], [15, 16], [19, 20, 21]] c = b.map {|a| a.length < 3 ? a : "#{a.first}-#{a.last}" } p c #=> [[1, 2], [4], "9-12", [15, 16], "19-21"] d = c.join(",") p d #=> "1,2,4,9-12,15,16,19-21"
Increasing (non-decreasing) subsequence can be chunked as follows:
a = [0, 9, 2, 2, 3, 2, 7, 5, 9, 5] p a.chunk_while {|i, j| i <= j }.to_a #=> [[0, 9], [2, 2, 3], [2, 7], [5, 9], [5]]
Adjacent evens and odds can be chunked as follows: (Enumerable#chunk is another way to do it.)
a = [7, 5, 9, 2, 0, 7, 9, 4, 2, 0] p a.chunk_while {|i, j| i.even? == j.even? }.to_a #=> [[7, 5, 9], [2, 0], [7, 9], [4, 2, 0]]
Enumerable#slice_when does the same, except splitting when the block returns true instead of false.
Sets create identifier, which is used to decide if the json_create hook of a class should be called; initial value is json_class:
JSON.create_id # => 'json_class'
Returns the current create identifier. See also JSON.create_id=.
Arguments obj and opts here are the same as arguments obj and opts in JSON.generate.
By default, generates JSON data without checking for circular references in obj (option max_nesting set to false, disabled).
Raises an exception if obj contains circular references:
a = []; b = []; a.push(b); b.push(a) # Raises SystemStackError (stack level too deep): JSON.fast_generate(a)
Arguments obj and opts here are the same as arguments obj and opts in JSON.generate.
Default options are:
{
indent: ' ', # Two spaces
space: ' ', # One space
array_nl: "\n", # Newline
object_nl: "\n" # Newline
}
Example:
obj = {foo: [:bar, :baz], bat: {bam: 0, bad: 1}} json = JSON.pretty_generate(obj) puts json
Output:
{
"foo": [
"bar",
"baz"
],
"bat": {
"bam": 0,
"bad": 1
}
}
Enters exclusive section and executes the block. Leaves the exclusive section automatically when the block exits. See example under MonitorMixin.
Returns the source file origin from the given object.
See ::trace_object_allocations for more information and examples.
Returns the original line from source for from the given object.
See ::trace_object_allocations for more information and examples.
Calls the block once for each living, nonimmediate object in this Ruby process. If module is specified, calls the block for only those classes or modules that match (or are a subclass of) module. Returns the number of objects found. Immediate objects (Fixnums, Symbols true, false, and nil) are never returned. In the example below, each_object returns both the numbers we defined and several constants defined in the Math module.
If no block is given, an enumerator is returned instead.
a = 102.7 b = 95 # Won't be returned c = 12345678987654321 count = ObjectSpace.each_object(Numeric) {|x| p x } puts "Total count: #{count}"
produces:
12345678987654321 102.7 2.71828182845905 3.14159265358979 2.22044604925031e-16 1.7976931348623157e+308 2.2250738585072e-308 Total count: 7
Takes a hash as its argument. The key is a symbol or an array of symbols. These symbols correspond to method names, instance variable names, or constant names (see def_delegator). The value is the accessor to which the methods will be delegated.
Takes a hash as its argument. The key is a symbol or an array of symbols. These symbols correspond to method names. The value is the accessor to which the methods will be delegated.