LEVIATHAN v962456e · 962456eee1

Standard Library

struct Triple<A, B, C>

A group of three values, possibly of different types.

since 0.1.0-alpha.1linuxwindowswasm

Overview

The three-field sibling of Pair, with the same conventions: it is a value type that is copied on assignment, and two triples are equal when all three fields are equal. Create one with Triple::Of(first, second, third). Use it when three values travel together and a purpose-built struct would be more than you need.

Description

Triple<A, B, C> holds three values in the fields first, second and third. Build one with Triple::Of(a, b, c). It follows the same conventions as Pair: it is a struct and therefore a value, copied on assignment, compared field by field with ==, and printed by toString() as (first, second, third).

Use a Triple where three values travel together briefly, such as a coordinate pair and a label, or a key with two related values. It saves writing a one-off struct and avoids nesting a Pair<A, Pair<B, C>>. When the three values carry a lasting meaning, a struct with named fields is clearer.

A point with a label

Triple<int, int, string> point = Triple::Of(3, 4, "home");
console.writeln(point.first + point.second);
console.writeln(point.third);
console.writeln(point.toString());
Triple<int, int, string> moved = point;
moved.first = 10;
console.writeln(point.first);
console.writeln(moved.first);
console.writeln(point == Triple::Of(3, 4, "home"));
console.writeln(point == moved);
Run it ▶
7
home
(3, 4, home)
3
10
true
false

Examples

An array of triples

Array<Triple<string, int, bool>> rows = [Triple::Of("ann", 30, true), Triple::Of("bob", 25, false)];
for (Triple<string, int, bool> row in rows) {
    console.writeln("${row.first} ${row.second} ${row.third}");
}
console.writeln(rows[1].toString());
Run it ▶
ann 30 true
bob 25 false
(bob, 25, false)

Examples

Typical use

Triple<string, int, float> row = Triple::Of("widget", 4, 2.5);
console.writeln("${row.first} x${row.second} @ ${row.third}");
console.writeln(row.toString());
console.writeln(row == Triple::Of("widget", 4, 2.5));
console.writeln(row == Triple::Of("widget", 5, 2.5));
Run it ▶
widget x4 @ 2.500000
(widget, 4, 2.500000)
true
false

Constructors

Of

Triple::Of(A a, B b, C c)

Create a triple from its three values.

Written Triple::Of(a, b, c); the type arguments are inferred from the declared type of the variable it is assigned to.

Parameters

a
The value for first.
b
The value for second.
c
The value for third.

Examples

Triple<int, string, float> t = Triple::Of(1, "x", 2.5);
console.writeln(t.first);
console.writeln(t.second);
console.writeln(t.third);
Run it ▶
1
x
2.500000

Fields

first

A first

The first value of the triple.

second

B second

The second value of the triple.

third

C third

The third value of the triple.

Methods

toString

toString() -> string

The triple as text, in the form (first, second, third).

This is what ${} interpolation of a triple produces. The fields are joined with +, so a field that is itself a struct is not expanded.

Returns

The text (first, second, third).

Examples

Triple<int, int, int> t = Triple::Of(1, 2, 3);
console.writeln(t.toString());
console.writeln("t = ${t}");
Run it ▶
(1, 2, 3)
t = (1, 2, 3)

Operators

==

==(Triple<A, B, C> other) -> bool

Compare two triples field by field.

The triples are equal when all three fields are equal, using the equality of the field types.

Parameters

other
The triple to compare with.

Returns

true if all three fields are equal.

Examples

Triple<int, int, int> a = Triple::Of(1, 2, 3);
console.writeln(a == Triple::Of(1, 2, 3));
console.writeln(a == Triple::Of(1, 2, 4));
console.writeln(a != Triple::Of(1, 2, 4));
Run it ▶
true
false
true

See also

  • Pair — A pair of two values, possibly of different types.