Range(B, E) - Crystal 1.21.0

# struct Range(B, E)

- Range(B, E)
- Struct
- Value
- Object

##
Overview

A `Range` represents an interval: a set of values with a beginning and an end.

Ranges may be constructed using the usual `.new` method or with literals:

    x..y  # an inclusive range, in mathematics: [x, y]
    x...y # an exclusive range, in mathematics: [x, y)
    (x..) # an endless range, in mathematics: >= x
    ..y   # a beginless inclusive range, in mathematics: <= y
    ...y  # a beginless exclusive range, in mathematics: < y

See `Range` literals in the language reference.

An easy way to remember which one is inclusive and which one is exclusive it to think of the extra dot as if it pushes y further away, thus leaving it outside of the range.

Ranges typically involve integers, but can be created using arbitrary objects as long as they define `succ` (or `pred` for `#reverse_each`), to get the next element in the range, and `<` and `#==`, to know when the range reached the end:

    # Represents a string of 'x's.
    struct Xs
      include Comparable(Xs)

      getter size

      def initialize(@size : Int32)
      end

      def succ
        Xs.new(@size + 1)
      end

      def <=>(other)
        @size <=> other.size
      end

      def inspect(io)
        @size.times { io << 'x' }
      end

      def to_s(io)
        io << @size << ' '
        inspect(io)
      end
    end

An example of using `Xs` to construct a range:

    r = Xs.new(3)..Xs.new(6)
    r.to_s                 # => "xxx..xxxxxx"
    r.to_a                 # => [Xs.new(3), Xs.new(4), Xs.new(5), Xs.new(6)]
    r.includes?(Xs.new(5)) # => true

##
Included Modules

- Enumerable(B)
- Iterable(B)

##
Defined in:

range.cr
range/bsearch.cr

##
Constructors

- .new(begin __arg0 : B, end __arg1 : E, exclusive : Bool = false)

  Constructs a `Range` using the given beginning and end.

##
Instance Method Summary

- #==(other : Range)
- #===(value)

  Same as `#includes?`, useful for the `case` expression.

- #begin : B

  Returns the object that defines the beginning of this range.

- #bsearch(&block : B | E -> _)

  By using binary search, returns the first element for which the passed block returns a truthy value.

- #clone

  Returns a new `Range` with `#begin` and `#end` cloned.

- #covers?(value)

  Same as `#includes?`.

- #cycle

  Returns an `Iterator` that cycles over the values of this range.

- #each(&) : Nil

  Iterates over the elements of this range, passing each in turn to the block.

- #each

  Returns an `Iterator` over the elements of this range.

- #end : E

  Returns the object that defines the end of the range.

- #excludes_end? : Bool

  Returns `true` if this range excludes the end element.

- #exclusive? : Bool

  Returns `true` if the range is exclusive.

- #includes?(value) : Bool

  Returns `true` if this range includes the given value.

- #inspect(io : IO) : Nil

  Appends this struct's name and instance variables names and values to the given IO.

- #map(&block : B -> U) forall U

  Returns an `Array` with the results of running the block against each element of the collection.

- #reverse_each(&) : Nil

  Iterates over the elements of this range in reverse order, passing each in turn to the block.

- #reverse_each

  Returns a reverse `Iterator` over the elements of this range.

- #sample(random : Random | Nil = nil)

  Optimized version of `Enumerable#sample` that runs in O(1) time when `self` is an `Int` or `Float` range.

- #sample(n : Int, random : Random | Nil = nil)

  Returns an `Array` of n random elements from `self`.

- #size : Int32

  Returns the number of values in this range.

- #step(by = 1, &) : Nil

  Iterates from `#begin` to `#end` incrementing by the amount of step on each iteration.

- #step(by = 1) : Iterator

  Iterates from `#begin` to `#end` incrementing by the amount of step on each iteration.

- #sum(initial)

  Optimized version of `Enumerable#sum` that runs in O(1) time when `self` is an `Int` range.

- #to_s(io : IO) : Nil

  Same as `#inspect(io)`.

### Instance methods inherited from module `Iterable(B)`

chunk(reuse = false, &block : T -> U) forall U chunk, chunk_while(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B chunk_while, cycle(n)
cycle cycle, each each, each_cons(count : Int, reuse = false) each_cons, each_cons_pair each_cons_pair, each_slice(count : Int, reuse = false) each_slice, each_step(n : Int)
each_step(n : Int, *, offset : Int) each_step, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object, slice_after(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_after(pattern, reuse : Bool | Array(T) = false) slice_after, slice_before(reuse : Bool | Array(T) = false, &block : T -> B) forall B
slice_before(pattern, reuse : Bool | Array(T) = false) slice_before, slice_when(reuse : Bool | Array(T) = false, &block : T, T -> B) forall B slice_when

### Instance methods inherited from module `Enumerable(B)`

accumulate(initial : U) : Array(U) forall U
accumulate : Array(T)
accumulate(initial : U, &block : U, T -> U) : Array(U) forall U
accumulate(&block : T, T -> T) : Array(T) accumulate, all?(& : T -> ) : Bool
all?(pattern) : Bool
all? : Bool all?, any?(& : T -> ) : Bool
any?(pattern) : Bool
any? : Bool any?, chunks(&block : T -> U) forall U chunks, compact_map(& : T -> _) compact_map, count(& : T -> ) : Int32
count(item) : Int32 count, cycle(n, & : T -> ) : Nil
cycle(& : T -> ) : Nil cycle, each(& : T -> ) each, each_cons(count : Int, reuse = false, &) each_cons, each_cons_pair(& : T, T -> ) : Nil each_cons_pair, each_slice(count : Int, reuse = false, &) each_slice, each_step(n : Int, *, offset : Int = 0, & : T -> ) : Nil each_step, each_with_index(offset = 0, &) each_with_index, each_with_object(obj : U, & : T, U -> ) : U forall U each_with_object, empty? : Bool empty?, find(if_none = nil, & : T -> ) find, find!(& : T -> ) : T find!, find_value(if_none = nil, & : T -> ) find_value, first(&)
first(count : Int) : Array(T)
first : T first, first? : T | Nil first?, flat_map(& : T -> _) flat_map, group_by(& : T -> U) forall U group_by, in_groups_of(size : Int, filled_up_with : U = nil) forall U
in_groups_of(size : Int, filled_up_with : U = nil, reuse = false, &) forall U in_groups_of, in_slices_of(size : Int) : Array(Array(T)) in_slices_of, includes?(obj) : Bool includes?, index(& : T -> ) : Int32 | Nil
index(obj) : Int32 | Nil index, index!(& : T -> ) : Int32
index!(obj) : Int32 index!, index_by(& : T -> U) : Hash(U, T) forall U index_by, join(io : IO, separator = "") : Nil
join(separator, io : IO) : Nil
join(separator = "") : String
join(io : IO, separator = "", & : T, IO -> )
join(separator, io : IO, &)
join(separator = "", & : T -> ) join, map(& : T -> U) : Array(U) forall U map, map_with_index(offset = 0, & : T, Int32 -> U) : Array(U) forall U map_with_index, max(count : Int) : Array(T)
max : T max, max? : T | Nil max?, max_by(& : T -> U) : T forall U max_by, max_by?(& : T -> U) : T | Nil forall U max_by?, max_of(& : T -> U) : U forall U max_of, max_of?(& : T -> U) : U | Nil forall U max_of?, min(count : Int) : Array(T)
min : T min, min? : T | Nil min?, min_by(& : T -> U) : T forall U min_by, min_by?(& : T -> U) : T | Nil forall U min_by?, min_of(& : T -> U) : U forall U min_of, min_of?(& : T -> U) : U | Nil forall U min_of?, minmax : Tuple(T, T) minmax, minmax? : Tuple(T | Nil, T | Nil) minmax?, minmax_by(& : T -> U) : Tuple(T, T) forall U minmax_by, minmax_by?(& : T -> U) : Tuple(T, T) | Tuple(Nil, Nil) forall U minmax_by?, minmax_of(& : T -> U) : Tuple(U, U) forall U minmax_of, minmax_of?(& : T -> U) : Tuple(U, U) | Tuple(Nil, Nil) forall U minmax_of?, none?(& : T -> ) : Bool
none?(pattern) : Bool
none? : Bool none?, one?(& : T -> ) : Bool
one?(pattern) : Bool
one? : Bool one?, partition(& : T -> ) : Tuple(Array(T), Array(T))
partition(type : U.class) forall U partition, present? : Bool present?, product(initial : Number)
product
product(initial : Number, & : T -> )
product(& : T -> _) product, reduce(memo, &)
reduce(&) reduce, reduce?(&) reduce?, reject(& : T -> )
reject(type : U.class) forall U
reject(pattern) : Array(T) reject, sample(n : Int, random : Random | Nil = nil) : Array(T)
sample(random : Random | Nil = nil) : T sample, select(& : T -> )
select(type : U.class) : Array(U) forall U
select(pattern) : Array(T) select, size : Int32 size, skip(count : Int) skip, skip_while(& : T -> ) : Array(T) skip_while, sum(initial)
sum
sum(initial, & : T -> )
sum(& : T -> ) sum, take_while(& : T -> ) : Array(T) take_while, tally(hash)
tally : Hash(T, Int32) tally, tally_by(hash, &)
tally_by(&block : T -> U) : Hash(U, Int32) forall U tally_by, to_a : Array(T)
to_a(& : T -> U) : Array(U) forall U to_a, to_h
to_h(& : T -> Tuple(K, V)) forall K, V to_h, to_set : Set(T)
to_set(&block : T -> U) : Set(U) forall U to_set, zip(*others : Indexable | Iterable | Iterator, &)
zip(*others : Indexable | Iterable | Iterator) zip, zip?(*others : Indexable | Iterable | Iterator, &)
zip?(*others : Indexable | Iterable | Iterator) zip?

### Class methods inherited from module `Enumerable(B)`

element_type(x) element_type

### Instance methods inherited from struct `Struct`

==(other : YAML::Any)
==(other) : Bool ==, hash(hasher) hash, inspect(io : IO) : Nil inspect, pretty_print(pp) : Nil pretty_print, to_s(io : IO) : Nil to_s

### Class methods inherited from struct `Struct`

pre_initialize(address : Pointer) : Nil pre_initialize

### Instance methods inherited from struct `Value`

==(other : Log::Metadata::Value)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io : String | IO, root : String)
from_json(string_or_io : String | IO) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Constructor Detail

def self.new(begin __arg0 : B, end __arg1 : E, exclusive : Bool = false) #

Constructs a `Range` using the given beginning and end.

    Range.new(1, 10)                  # => 1..10
    Range.new(1, 10, exclusive: true) # => 1...10

##
Instance Method Detail

def ==(other : Range) #
def ===(value) #

Same as `#includes?`, useful for the `case` expression.

    case 79
    when 1..50   then puts "low"
    when 51..75  then puts "medium"
    when 76..100 then puts "high"
    end

Produces:

    high

See also: `Object#===`.

def begin : B #

Returns the object that defines the beginning of this range.

    (1..10).begin  # => 1
    (1...10).begin # => 1

def bsearch(&block : B | E -> _) #

By using binary search, returns the first element for which the passed block returns a truthy value.

If the block returns a falsey value, the element to be found lies behind. If the block returns a truthy value, the element to be found is itself or lies in front.

Returns `nil` if the block didn't return a truthy value for any element.

    (0..10).bsearch { |x| x >= 5 }                       # => 5
    (0..Float64::INFINITY).bsearch { |x| x ** 4 >= 256 } # => 4

def clone #

Returns a new `Range` with `#begin` and `#end` cloned.

def covers?(value) #

Same as `#includes?`.

def cycle #

Returns an `Iterator` that cycles over the values of this range.

    (1..3).cycle.first(5).to_a # => [1, 2, 3, 1, 2]

def each(&) : Nil #

Iterates over the elements of this range, passing each in turn to the block.

    (10..15).each { |n| print n, ' ' }
    # prints: 10 11 12 13 14 15

def each #

Returns an `Iterator` over the elements of this range.

    (1..3).each.skip(1).to_a # => [2, 3]

def end : E #

Returns the object that defines the end of the range.

    (1..10).end  # => 10
    (1...10).end # => 10

def excludes_end? : Bool #

Returns `true` if this range excludes the end element.

    (1..10).excludes_end?  # => false
    (1...10).excludes_end? # => true

def exclusive? : Bool #

Returns `true` if the range is exclusive. Returns `false` otherwise (default).

def includes?(value) : Bool #

Returns `true` if this range includes the given value.

    (1..10).includes?(4)  # => true
    (1..10).includes?(10) # => true
    (1..10).includes?(11) # => false

    (1...10).includes?(9)  # => true
    (1...10).includes?(10) # => false

def inspect(io : IO) : Nil #
Description copied from struct Struct

Appends this struct's name and instance variables names and values to the given IO.

    struct Point
      def initialize(@x : Int32, @y : Int32)
      end
    end

    p1 = Point.new 1, 2
    p1.to_s    # "Point(@x=1, @y=2)"
    p1.inspect # "Point(@x=1, @y=2)"

def map(&block : B -> U) forall U #
Description copied from module Enumerable(B)

Returns an `Array` with the results of running the block against each element of the collection.

    [1, 2, 3].map { |i| i * 10 } # => [10, 20, 30]

def reverse_each(&) : Nil #

Iterates over the elements of this range in reverse order, passing each in turn to the block.

    (10...15).reverse_each { |n| print n, ' ' }
    # prints: 14 13 12 11 10

def reverse_each #

Returns a reverse `Iterator` over the elements of this range.

    (1..3).reverse_each.skip(1).to_a # => [2, 1]

def sample(random : Random | Nil = nil) #

Optimized version of `Enumerable#sample` that runs in O(1) time when `self` is an `Int` or `Float` range. In these cases, this range is considered to be a distribution of numeric values rather than a collection of elements, and the method simply calls `random.rand(self)`.

Raises `ArgumentError` if `self` is an open range.

def sample(n : Int, random : Random | Nil = nil) #

Returns an `Array` of n random elements from `self`. All elements have equal probability of being drawn. Sampling is done without replacement; if n is larger than the size of this collection, the returned `Array` has the same size as `self`.

Raises `ArgumentError` if n is negative.

    [1, 2, 3, 4, 5].sample(2) # => [3, 5]
    {1, 2, 3, 4, 5}.sample(2) # => [3, 4]

Uses the random instance when provided if the randomness needs to be controlled or to follow some traits. For example the following calls use a custom seed or a secure random source:

    {1, 2, 3, 4, 5}.sample(2, Random.new(1))  # => [1, 5]
    {1, 2, 3, 4, 5}.sample(2, Random::Secure) # => [2, 5]

If `self` is not empty and `n` is equal to 1, calls `#sample(random)` exactly once. Thus, random will be left in a different state compared to the implementation in `Enumerable`.

def size : Int32 #

Returns the number of values in this range.

If both the beginning and the end of this range are `Int`s, runs in constant time instead of linear.

    (3..8).size  # => 6
    (3...8).size # => 5

Raises `OverflowError` if the difference is bigger than `Int32`. Raises `ArgumentError` if either `#begin` or `#end` are `nil`.

def step(by = 1, &) : Nil #

Iterates from `#begin` to `#end` incrementing by the amount of step on each iteration.

    ary = [] of Int32
    (1..4).step(by: 2) do |x|
      ary << x
    end
    ary                      # => [1, 3]
    (1..4).step(by: 2).to_a  # => [1, 3]
    (1..4).step(by: 1).to_a  # => [1, 2, 3, 4]
    (1...4).step(by: 1).to_a # => [1, 2, 3]

If `B` is a `Steppable`, implementation is delegated to `Steppable#step`. Otherwise `#succ` method is expected to be defined on `#begin` and its successors and iteration is based on calling `#succ` sequentially (step times per iteration).

Raises `ArgumentError` if `#begin` is `nil`.

def step(by = 1) : Iterator #

Iterates from `#begin` to `#end` incrementing by the amount of step on each iteration.

    ary = [] of Int32
    (1..4).step(by: 2) do |x|
      ary << x
    end
    ary                      # => [1, 3]
    (1..4).step(by: 2).to_a  # => [1, 3]
    (1..4).step(by: 1).to_a  # => [1, 2, 3, 4]
    (1...4).step(by: 1).to_a # => [1, 2, 3]

If `B` is a `Steppable`, implementation is delegated to `Steppable#step`. Otherwise `#succ` method is expected to be defined on `#begin` and its successors and iteration is based on calling `#succ` sequentially (step times per iteration).

Raises `ArgumentError` if `#begin` is `nil`.

def sum(initial) #

Optimized version of `Enumerable#sum` that runs in O(1) time when `self` is an `Int` range.

def to_s(io : IO) : Nil #
Description copied from struct Struct

Same as `#inspect(io)`.