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struct Tuple(*T)
inherits Value

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.

Indexing with a range literal known at compile-time is also allowed, and the returned value will have the correct sub-tuple type:

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

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

Comparable Indexable

Class methods

.types

Returns the types of this tuple type.

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

.from(array : Array) : self

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.

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

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.new(pull : JSON::PullParser)

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.new(*args : *T)

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
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Methods

#+(other : Tuple)

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)
View source

#<=>(other : Tuple)

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
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#<=>(other : self)

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
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#==(other)

Returns false.

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#==(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
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#==(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
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#===(other : self)

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#===.

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#===(other : Tuple)

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#===.

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#[](range : Range)

Returns all elements that are within the given range. range must be a range literal whose value is known at compile-time.

Negative indices count backward from the end of the array (-1 is the last element). Additionally, an empty array is returned when the starting index for an element range is at the end of the array.

Raises a compile-time error if range.begin is out of range.

tuple = {1, "hello", 'x'}
tuple[0..1] # => {1, "hello"}
tuple[-2..] # => {"hello", 'x'}
tuple[...1] # => {1}
tuple[4..]  # Error: begin index out of bounds for Tuple(Int32, Char, Array(Int32), String) (5 not in -4..4)

i = 0
tuple[i..2] # Error: Tuple#[](Range) can only be called with range literals known at compile-time

i = 0..2
tuple[i] # Error: Tuple#[](Range) can only be called with range literals known at compile-time
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#[](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] # raises IndexError
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#[]?(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
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#at(index : Int

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
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#at(index : Int)

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
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#clone

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

View source

#each(&) : Nil

Yields each of the elements in this tuple.

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

Output:

1
"hello"
'x'
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#first

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

tuple = {1, 2.5}
tuple.first # => 1
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#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
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#from(array : Array)

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"
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#hash(hasher)

See Object#hash(hasher)

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#inspect : String

Same as to_s.

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#last

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

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

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"}
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#map_with_index(offset = 0

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"}

Accepts an optional offset parameter, which tells it to start counting from there.

View source

#pretty_print(pp) : Nil

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#reverse

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

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

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
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#size

Returns the number of elements in this tuple.

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

Returns an Array with all the elements in the collection.

{1, 2, 3}.to_a # => [1, 2, 3]
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#to_json(json : JSON::Builder)

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#to_s(io : IO) : Nil

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

tuple = {1, "hello"}
tuple.to_s # => "{1, \"hello\"}"
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#to_yaml(yaml : YAML::Nodes::Builder)

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#unsafe_fetch(index : Int)

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.

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