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/Crystal 0.31

struct Tuple(*T)

Overview

A tuple is a fixed-size, immutable, stack-allocated sequence of values of possibly different types.

You can think of a Tuple as an immutable Array whose types for each position are known at compile time.

A tuple can be created with the usual .new method or with a tuple literal:

tuple = {1, "hello", 'x'} # Tuple(Int32, String, Char)
tuple[0]                  # => 1
tuple[1]                  # => "hello"
tuple[2]                  # => 'x'

The compiler knows what types are in each position, so when indexing a tuple with an integer literal the compiler will return the value in that index and with the expected type, like in the above snippet. Indexing with an integer literal outside the bounds of the tuple will give a compile-time error.

Indexing with an integer value that is only known at runtime will return a value whose type is the union of all the types in the tuple, and might raise IndexError.

Tuples are the preferred way to return fixed-size multiple return values because no memory is needed to be allocated for them:

def one_and_hello
  {1, "hello"}
end

one, hello = one_and_hello
one   # => 1
hello # => "hello"

Good examples of the above are Number#divmod and Enumerable#minmax.

Tuples can be splat with the * operator and passed to methods:

def multiply(string, value)
  string * value
end

tuple = {"hey", 2}
value = multiply(*tuple) # same as multiply tuple[0], tuple[1]
value                    # => "heyhey"

Finally, when using a splat argument in a method definition its type will be a tuple of the call arguments:

def splat_test(*args)
  args
end

tuple = splat_test 1, "hello", 'x'
tuple.class # => Tuple(Int32, String, Char)
tuple       # => {1, "hello", 'x'}

Included Modules

Defined in:

tuple.cr
json/to_json.cr
yaml/to_yaml.cr

Constructors

Class Method Summary

  • .types

    Returns the types of this tuple type.

Instance Method Summary

Instance methods inherited from module Comparable(Tuple(*T))

<, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) >, >=(other : T) >=

Instance methods inherited from module Indexable(Union(*T))

[](index : Int) [], []?(index : Int) []?, bsearch(&block : Union(T) -> Bool) bsearch, bsearch_index(&block : Union(T), Int32 -> Bool) bsearch_index, dig(index : Int, *subindexes) dig, dig?(index : Int, *subindexes) dig?, each(*, start : Int, count : Int, &block)
each(*, within range : Range, &block)
each(&block)
each each
, each_index(*, start : Int, count : Int, &block)
each_index(&block) : Nil
each_index each_index
, empty? empty?, equals?(other : Indexable, &block)
equals?(other, &block) equals?
, fetch(index, default)
fetch(index : Int, &block) fetch
, first
first(&block) first
, first? first?, hash(hasher) hash, index(object, offset : Int = 0)
index(offset : Int = 0, &block) index
, join(separator = "") join, last
last(&block) last
, last? last?, reverse_each(&block) : Nil
reverse_each reverse_each
, rindex(offset = size - 1, &block)
rindex(value, offset = size - 1) rindex
, sample(random = Random::DEFAULT) sample, size size, to_a to_a, unsafe_fetch(index : Int) unsafe_fetch, values_at(*indexes : Int) values_at

Instance methods inherited from module Enumerable(Union(*T))

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

Instance methods inherited from module Iterable(Union(*T))

chunk(reuse = false, &block : Union(T) -> U) forall U chunk, chunk_while(reuse : Bool | Array(Union(T)) = false, &block : Union(T), Union(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(Union(T)) = false, &block : Union(T) -> B) forall B
slice_after(pattern, reuse : Bool | Array(Union(T)) = false) slice_after
, slice_before(reuse : Bool | Array(Union(T)) = false, &block : Union(T) -> B) forall B
slice_before(pattern, reuse : Bool | Array(Union(T)) = false) slice_before
, slice_when(reuse : Bool | Array(Union(T)) = false, &block : Union(T), Union(T) -> B) forall B slice_when

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) =~, class class, dup dup, hash(hasher)
hash hash
, inspect(io : IO) : Nil
inspect : String 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(&block) 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(&block) try, unsafe_as(type : T.class) forall T unsafe_as

Constructor methods inherited from class Object

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

Constructor Detail

def self.from(array : Array) : selfSource

Creates a tuple from the given array, with elements casted to the given types.

Tuple(String, Int64).from(["world", 2_i64])       # => {"world", 2_i64}
Tuple(String, Int64).from(["world", 2_i64]).class # => Tuple(String, Int64)

See also: #from.

def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)Source

def self.new(pull : JSON::PullParser)Source

def self.new(*args : *T)Source

Creates a tuple that will contain the given values.

This method is useful in macros and generic code because with it you can create empty tuples, something that you can't do with a tuple literal.

Tuple.new(1, "hello", 'x') #=> {1, "hello", 'x'}
Tuple.new                  #=> {}

{}                         # syntax error

Class Method Detail

def self.typesSource

Returns the types of this tuple type.

tuple = {1, "hello", 'x'}
tuple.class.types # => {Int32, String, Char}

Instance Method Detail

def +(other : Tuple)Source

Returns a tuple that contains self's elements followed by other's elements.

t1 = {1, 2}
t2 = {"foo", "bar"}
t3 = t1 + t2
t3         # => {1, 2, "foo", "bar"}
typeof(t3) # => Tuple(Int32, Int32, String, String)

def <=>(other : self)Source

The comparison operator.

Each object in each tuple is compared using the #<=> operator.

Tuples are compared in an "element-wise" manner; the first element of this tuple is compared with the first one of other using the #<=> operator, then each of the second elements, etc. As soon as the result of any such comparison is non-zero (i.e. the two corresponding elements are not equal), that result is returned for the whole tuple comparison.

If all the elements are equal, then the result is based on a comparison of the tuple sizes. Thus, two tuples are "equal" according to #<=> if, and only if, they have the same size and the value of each element is equal to the value of the corresponding element in the other tuple.

{"a", "a", "c"} <=> {"a", "b", "c"} # => -1
{1, 2, 3, 4, 5, 6} <=> {1, 2}       # => 1
{1, 2} <=> {1, 2.0}                 # => 0

def <=>(other : Tuple)Source

The comparison operator.

Each object in each tuple is compared using the #<=> operator.

Tuples are compared in an "element-wise" manner; the first element of this tuple is compared with the first one of other using the #<=> operator, then each of the second elements, etc. As soon as the result of any such comparison is non-zero (i.e. the two corresponding elements are not equal), that result is returned for the whole tuple comparison.

If all the elements are equal, then the result is based on a comparison of the tuple sizes. Thus, two tuples are "equal" according to #<=> if, and only if, they have the same size and the value of each element is equal to the value of the corresponding element in the other tuple.

{"a", "a", "c"} <=> {"a", "b", "c"} # => -1
{1, 2, 3, 4, 5, 6} <=> {1, 2}       # => 1
{1, 2} <=> {1, 2.0}                 # => 0

def ==(other : self)Source

Returns true if this tuple has the same size as the other tuple and their elements are equal to each other when compared with #==.

t1 = {1, "hello"}
t2 = {1.0, "hello"}
t3 = {2, "hello"}

t1 == t2 # => true
t1 == t3 # => false

def ==(other : Tuple)Source

Returns true if this tuple has the same size as the other tuple and their elements are equal to each other when compared with #==.

t1 = {1, "hello"}
t2 = {1.0, "hello"}
t3 = {2, "hello"}

t1 == t2 # => true
t1 == t3 # => false

def ==(other)Source

Description copied from struct Value

Returns false.

def ===(other : self)Source

Returns true if case equality holds for the elements in self and other.

{1, 2} === {1, 2} # => true
{1, 2} === {1, 3} # => false

See also: Object#===.

def ===(other : Tuple)Source

Returns true if self and other have the same size and case equality holds for the elements in self and other.

{1, 2} === {1, 2, 3}             # => false
{/o+/, "bar"} === {"foo", "bar"} # => true

See also: Object#===.

def [](index : Int)Source

Returns the element at the given index. Read the type docs to understand the difference between indexing with a number literal or a variable.

tuple = {1, "hello", 'x'}
tuple[0] # => 1 (Int32)
tuple[3] # compile error: index out of bounds for tuple {Int32, String, Char}

i = 0
tuple[i] # => 1 (Int32 | String | Char)

i = 3
tuple[i] # raises IndexError

def []?(index : Int)Source

Returns the element at the given index or nil if out of bounds.

tuple = {1, "hello", 'x'}
tuple[0]? # => 1
tuple[3]? # => nil

def at(index : Int)Source

Returns the element at the given index or raises IndexError if out of bounds.

tuple = {1, "hello", 'x'}
tuple.at(0) # => 1
tuple.at(3) # raises IndexError

def at(index : Int, &block)Source

Returns the element at the given index or the value returned by the block if out of bounds.

tuple = {1, "hello", 'x'}
tuple.at(0) { 10 } # => 1
tuple.at(3) { 10 } # => 10

def cloneSource

Returns a tuple containing cloned elements of this tuple using the #clone method.

def each(&block) : NilSource

Yields each of the elements in this tuple.

tuple = {1, "hello", 'x'}
tuple.each do |value|
  puts value
end

Output:

1
"hello"
'x'

def firstSource

Returns the first element of this tuple. Doesn't compile if the tuple is empty.

tuple = {1, 2.5}
tuple.first # => 1

def first?Source

Returns the first element of this tuple, or nil if this is the empty tuple.

tuple = {1, 2.5}
tuple.first? # => 1

empty = Tuple.new
empty.first? # => nil

def from(array : Array)Source

Expects to be called on a tuple of types, creates a tuple from the given array, with types casted appropriately.

This allows you to easily pass an array as individual arguments to a method.

require "json"

def speak_about(thing : String, n : Int64)
  "I see #{n} #{thing}s"
end

data = JSON.parse(%(["world", 2])).as_a.map(&.raw)
speak_about(*{String, Int64}.from(data)) # => "I see 2 worlds"

def hash(hasher)Source

def inspect : StringSource

Same as #to_s.

def lastSource

Returns the last element of this tuple. Doesn't compile if the tuple is empty.

tuple = {1, 2.5}
tuple.last # => 2.5

def last?Source

Returns the last element of this tuple, or nil if this is the empty tuple.

tuple = {1, 2.5}
tuple.last? # => 2.5

empty = Tuple.new
empty.last? # => nil

def map(&block)Source

Returns a new tuple where elements are mapped by the given block.

tuple = {1, 2.5, "a"}
tuple.map &.to_s # => {"1", "2.5", "a"}

def map_with_index(&block)Source

Like #map, but the block gets passed both the element and its index.

tuple = {1, 2.5, "a"}
tuple.map_with_index { |e, i| "tuple[#{i}]: #{e}" } # => {"tuple[0]: 1", "tuple[1]: 2.5", "tuple[2]: a"}

def pretty_print(pp) : NilSource

def reverseSource

Returns a new tuple where the elements are in reverse order.

tuple = {1, 2.5, "a"}
tuple.reverse # => {"a", 2.5, 1}

def reverse_each(&block)Source

Yields each of the elements in this tuple in reverse order.

tuple = {1, "hello", 'x'}
tuple.reverse_each do |value|
  puts value
end

Output:

'x'
"hello"
1

def sizeSource

Returns the number of elements in this tuple.

{'a', 'b'}.size # => 2

def to_json(json : JSON::Builder)Source

def to_s(io : IO) : NilSource

Appends a string representation of this tuple to the given IO.

tuple = {1, "hello"}
tuple.to_s # => "{1, \"hello\"}"

def to_yaml(yaml : YAML::Nodes::Builder)Source

def unsafe_fetch(index : Int)Source

Description copied from module Indexable(Union(*T))

Returns the element at the given index, without doing any bounds check.

Indexable makes sure to invoke this method with index in 0...size, so converting negative indices to positive ones is not needed here.

Clients never invoke this method directly. Instead, they access elements with #[](index) and #[]?(index).

This method should only be directly invoked if you are absolutely sure the index is in bounds, to avoid a bounds check for a small boost of performance.

© 2012–2019 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.31.1/Tuple.html