# 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

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:

##
Constructors

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

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

##
Instance Method Summary

- #===(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 -> Bool)

  By using binary search, returns the first value for which the passed block returns `true`.

- #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?

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

- #exclusive? : Bool

  Returns `true` if the range is exclusive.

- #includes?(value)

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

- #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.

- #step(by = 1)

  Returns an `Iterator` that returns each nth element in this range.

- #step(by = 1, &)

  Iterates over this range, passing each nth element to the block.

- #sum(initial)

  If `self` is a `Int` range, it provides O(1) implementation, otherwise it is same as `Enumerable#sum`.

### 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_slice(count : Int, reuse = false) each_slice, 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)`

all?(&)
all?(pattern)
all? all?, any?(&)
any?(pattern)
any? any?, chunks(&block : T -> U) forall U chunks, compact_map(&) compact_map, count(&)
count(item) count, cycle(n, &)
cycle(&) cycle, each(&block : 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_with_index(offset = 0, &) each_with_index, each_with_object(obj, &) each_with_object, find(if_none = nil, &) find, first(count : Int)
first first, first? first?, flat_map(&block : T -> Array(U) | Iterator(U) | U) forall U flat_map, grep(pattern) grep, group_by(&block : 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, includes?(obj) includes?, index(&)
index(obj) index, index_by(&block : T -> U) forall U index_by, join(separator = "", &)
join(separator, io, &)
join(separator, io)
join(separator = "") join, map(&block : T -> U) forall U map, map_with_index(offset = 0, &block : T, Int32 -> U) forall U map_with_index, max max, max? max?, max_by(&block : T -> U) forall U max_by, max_by?(&block : T -> U) forall U max_by?, max_of(&block : T -> U) forall U max_of, max_of?(&block : T -> U) forall U max_of?, min min, min? min?, min_by(&block : T -> U) forall U min_by, min_by?(&block : T -> U) forall U min_by?, min_of(&block : T -> U) forall U min_of, min_of?(&block : T -> U) forall U min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) forall U minmax_by, minmax_by?(&block : T -> U) forall U minmax_by?, minmax_of(&block : T -> U) forall U minmax_of, minmax_of?(&block : T -> U) forall U minmax_of?, none?
none?(pattern)
none?(&) none?, one?(&)
one?(pattern)
one? one?, partition(&) partition, product(&)
product(initial : Number, &)
product
product(initial : Number) product, reduce(memo, &)
reduce(&) reduce, reduce?(&) reduce?, reject(&block : T -> )
reject(type : U.class) forall U
reject(pattern) reject, select(pattern)
select(type : U.class) forall U
select(&block : T -> ) select, size size, skip(count : Int) skip, skip_while(&) skip_while, sum(initial)
sum
sum(initial, &)
sum(&) sum, take_while(&) take_while, tally : Hash(T, Int32) tally, to_a to_a, to_h
to_h(&block : T -> Tuple(K, V)) forall K, V to_h, to_set to_set, zip(*others : Indexable | Iterable | Iterator, &)
zip(*others : Indexable | Iterable | Iterator) zip, zip?(*others : Indexable | Iterable | Iterator, &)
zip?(*others : Indexable | Iterable | Iterator) zip?

### Instance methods inherited from struct `Struct`

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

### Instance methods inherited from struct `Value`

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, __crystal_pseudo_! : Bool __crystal_pseudo_!, __crystal_pseudo_as(type : Class) __crystal_pseudo_as, __crystal_pseudo_as?(type : Class) __crystal_pseudo_as?, __crystal_pseudo_is_a?(type : Class) : Bool __crystal_pseudo_is_a?, __crystal_pseudo_nil? : Bool __crystal_pseudo_nil?, __crystal_pseudo_responds_to?(name : Symbol) : Bool __crystal_pseudo_responds_to?, class class, dup dup, hash(hasher)
hash hash, inspect : String
inspect(io : IO) : Nil inspect, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&) tap, to_json(io : IO)
to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s : String
to_s(io : IO) : Nil to_s, to_yaml(io : IO)
to_yaml to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

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

##
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 ===(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 -> Bool) #

By using binary search, returns the first value for which the passed block returns `true`.

If the block returns `false`, the finding value exists behind. If the block returns `true`, the finding value is itself or exists infront.

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

Returns `nil` if the block didn't return `true` for any value.

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? #

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) #

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 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 step(by = 1) #

Returns an `Iterator` that returns each nth element in this range.

    (1..10).step(3).skip(1).to_a # => [4, 7, 10]

def step(by = 1, &) #

Iterates over this range, passing each nth element to the block.

    range = Xs.new(1)..Xs.new(10)
    range.step(2) { |x| puts x }
    puts
    range.step(3) { |x| puts x }

Produces:

    1 x
    3 xxx
    5 xxxxx
    7 xxxxxxx
    9 xxxxxxxxx

    1 x
    4 xxxx
    7 xxxxxxx
    10 xxxxxxxxxx

See `Range`'s overview for the definition of `Xs`.

def sum(initial) #

If `self` is a `Int` range, it provides O(1) implementation, otherwise it is same as `Enumerable#sum`.