struct Tuple(T*)

Overview

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

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       (Int32)
tuple[1]                  # => "hello" (String)
tuple[2]                  # => 'x'     (Char)

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

Included Modules

Defined in:

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

Class Method Summary

Instance Method Summary

Instance methods inherited from module Comparable(T)

<(other : T) <, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) >, >=(other : T) >=, between?(min, max) between?

Instance methods inherited from module Iterable

cycle
cycle(n)
cycle
, each each, each_cons(count : Int) each_cons, each_slice(count : Int) each_slice, each_with_index(offset = 0) each_with_index, each_with_object(obj) each_with_object

Instance methods inherited from module Enumerable(T)

all?
all?(&block)
all?
, any?
any?(&block)
any?
, compact_map(&block) compact_map, count(item)
count(&block)
count
, cycle(&block)
cycle(n, &block)
cycle
, each(&block : T -> _) each, each_cons(count : Int, &block) each_cons, each_slice(count : Int, &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 first, first? first?, flat_map(&block : T -> Array(U)) flat_map, grep(pattern) grep, group_by(&block : T -> U) group_by, in_groups_of(size : Int, filled_up_with = nil, &block)
in_groups_of(size : Int, filled_up_with = nil)
in_groups_of
, includes?(obj) includes?, index(obj)
index(&block)
index
, index_by(&block : T -> U) index_by, join(separator = "")
join(separator, io, &block)
join(separator = "", &block)
join(separator, io)
join
, map(&block : T -> U) map, map_with_index(&block : T, Int32 -> U) map_with_index, max max, max? max?, max_by(&block : T -> U) max_by, max_by?(&block : T -> U) max_by?, max_of(&block : T -> U) max_of, max_of?(&block : T -> U) max_of?, min min, min? min?, min_by(&block : T -> U) min_by, min_by?(&block : T -> U) min_by?, min_of(&block : T -> U) min_of, min_of?(&block : T -> U) min_of?, minmax minmax, minmax? minmax?, minmax_by(&block : T -> U) minmax_by, minmax_by?(&block : T -> U) minmax_by?, minmax_of(&block : T -> U) minmax_of, minmax_of?(&block : T -> U) minmax_of?, none?(&block)
none?
none?
, one?(&block) one?, partition(&block) partition, reduce(&block)
reduce(memo, &block)
reduce
, reject(&block : T -> ) reject, select(&block : T -> ) select, size size, skip(count : Int) skip, skip_while(&block) skip_while, sum(initial, &block)
sum(&block)
sum(initial)
sum
sum
, take(count : Int) take, take_while(&block) take_while, to_a to_a, to_h to_h, to_set to_set

Instance methods inherited from struct Value

! !, ==(other) ==, nil? nil?

Instance methods inherited from class Object

! !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other) ===, =~(other) =~, class class, clone clone, crystal_type_id crystal_type_id, dup dup, hash hash, inspect
inspect(io : IO)
inspect
, itself itself, not_nil! not_nil!, tap(&block) tap, to_json to_json, to_pretty_json(io : IO)
to_pretty_json
to_pretty_json
, to_s
to_s(io : IO)
to_s
, to_yaml(io : IO)
to_yaml
to_yaml
, try(&block) try

Class methods inherited from class Object

==(other : Class) ==, ===(other) ===, cast(other) : self cast, from_json(string_or_io) from_json, from_yaml(string : String) from_yaml, hash hash, inspect(io) inspect, name : String name, to_s(io) to_s

Class Method Detail

def self.new(*args) #

Creates a tuple that will contain the given arguments.

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

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

{}                         # syntax error

[View source]
def self.new(pull : YAML::PullParser) #

[View source]
def self.new(pull : JSON::PullParser) #

[View source]

Instance Method Detail

def <=>(other : Tuple) #

Implements 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

See Object#<=>.


[View source]
def <=>(other : self) #

Implements 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

See Object#<=>.


[View source]
def ==(other : Tuple) #

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

[View source]
def ==(other : self) #

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

[View source]
def [](index : Int) #

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] # => runtime error: IndexError

[View source]
def []?(index : Int) #

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

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

[View source]
def at(index : Int, &block) #

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

[View source]
def at(index : Int) #

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

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

[View source]
def clone #

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


[View source]
def dup #

Returns self.


[View source]
def each(&block) #

Yields each of the elements in this tuple.

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

Output:

1
"hello"
'x'

[View source]
def each #

Returns an Iterator for the elements in this tuple.

{1, 'a'}.each.cycle.take(3).to_a # => [1, 'a', 1]

[View source]
def empty? #

Returns true if this tuple is empty.

Tuple.new.empty? # => true
{1, 2}.empty?    # => false

[View source]
def first #

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

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

[View source]
def first? #

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

[View source]
def hash #

returns a hash value based on this tuple's length and contents.

see object#hash.


[View source]
def inspect #

Same as #to_s.


[View source]
def last #

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

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

[View source]
def last? #

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

[View source]
def map(&block) #

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"}

[View source]
def reverse #

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

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

[View source]
def size #

Returns the number of elements in this tuple.

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

[View source]
def to_json(io) #

[View source]
def to_s(io) #

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

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

[View source]
def to_yaml(yaml : YAML::Generator) #

[View source]
def types #

Returns a tuple containing the types of this tuple.

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

[View source]
def values_at(*indexes : Int) #

Returns a tuple populated with the elements at the given indexes. Raises if any index is invalid.

{"a", "b", "c", "d"}.values_at(0, 2) # => {"a", "c"}

[View source]