Julia Tuples

A tuple is a fixed collection of values grouped in parentheses. Once a tuple is created, its values cannot be changed.

A tuple groups values in parentheses

The tuple holds a number and a string together. Indexes read the values back one at a time.

t = (1, "one")
println(t)
println(t[1])
println(t[2])

A named tuple reads fields by name

Each value in a named tuple carries a name. A dot followed by the name reads that field.

t = (name = "Ana", age = 31)
println(t)
println(t.name)
println(t.age)

Several return values arrive as a tuple

A function can return several values with one return line. The caller receives them together as a tuple.

function splitnum(n)
    return div(n, 10), n % 10
end
pair = splitnum(47)
println(pair)
println(pair[1])
println(pair[2])

Example

function lowhigh(x, y)
    return min(x, y), max(x, y)
end
result = lowhigh(9, 4)
println(result)
println(result[1])
person = (name = "Bo", age = 28)
println(person.name)
println(person.age)

Key points

Tuple literal: values in parentheses, separated by commas, like (1, "one").
Indexing: t[1] gives the first value and t[2] gives the second value.
Fixed: a tuple cannot be changed after it is created.
Named tuple: (name = "Ana", age = 31) gives each value a name.
Field access: t.name reads the value stored under the name name.
Return values: a function can return several values at once, and they arrive as a tuple.

In this example, lowhigh returns the smaller and larger of its two inputs as one tuple, so result is (4, 9) and result[1] is 4. The named tuple person then shows field access, printing the name Bo and the age 28.

Try it Yourself

Edit the code, then press Run.

Running is simulated · JuliaHub

function lowhigh(x, y)
    return min(x, y), max(x, y)
end
result = lowhigh(9, 4)
println(result)
println(result[1])
person = (name = "Bo", age = 28)
println(person.name)
println(person.age)

Exercise

For t = (name = "Ana", age = 31), what does t.age give?

31 "Ana" age (name = "Ana", age = 31)