Tuples and Named Tuples

A tuple is a fixed-size, immutable group of values, written with parentheses:

point = (3, 4)
println(point[1], " ", point[2], " ", length(point))
println(typeof(point))
x, y = point
println("x=$x y=$y")
mixed = ("Ada", 36, true)
println(typeof(mixed))
single = (42,)
println(typeof(single))

3 4 2
Tuple{Int64, Int64}
x=3 y=4
Tuple{String, Int64, Bool}
Tuple{Int64}

• A tuple's type records the type of each element.
• Destructuring: x, y = point unpacks a tuple into variables.
• A one-element tuple needs a trailing comma: (42,).
• Tuples can't be changed after creation — point[1] = 5 is an error. That makes them cheap and fast.

Named tuples

A named tuple gives each value a name:

person = (name = "Ada", born = 1815)
println(person.name, " ", person[:born], " ", person[2])
println(keys(person))
println(person)

older = (; person..., born = 1800)
println(older)

name = "Grace"; born = 1906
p2 = (; name, born)
println(p2)

Ada 1815 1815
(:name, :born)
(name = "Ada", born = 1815)
(name = "Ada", born = 1800)
(name = "Grace", born = 1906)

• Access fields with .name, by symbol [:name], or by position.
• (; person..., born = 1800) makes a copy with one field changed.
• (; name, born) builds a named tuple from variables with the same names.

Returning several values

Functions return several values by returning a tuple:

function min_max(xs)
    return minimum(xs), maximum(xs)
end

lo, hi = min_max([5, 3, 9, 1])
println(lo, " ", hi)
stats = (count = 4, mean = 4.5)
println("n=$(stats.count), mean=$(stats.mean)")

1 9
n=4, mean=4.5

Named tuples are a lightweight way to return labeled results without defining a new type.