Display

The interface for converting a value to a String.

Module: Std

Interface

interface Display {
    func ToString() -> String;
}

A type implements Display by providing a ToString method. Any Display value can be passed to Print, PrintLine, and Format, which is how those functions accept mixed argument types through the variadic Display... parameter.

Implementing Display

Implement the interface with an extend ... : Display block:

import Std::Display;

struct Point {
    x: int;
    y: int;
}

extend Point : Display {
    func ToString(self) -> String {
        return Format("({}, {})", self.x, self.y);
    }
}

Once implemented, a Point can be printed or formatted directly:

let p = Point { x: 3, y: 4 };
PrintLine(p);              // (3, 4)
let s = Format("p = {}", p);

Built-in implementations

The standard library implements Display for every built-in numeric, boolean, and character type, as well as for String and StringBuilder:

Category	Types
Signed	int, int8, int16, int32, int64
Unsigned	uint, uint8, uint16, uint32, uint64
Float	float32, float64
Boolean	bool, bool8, bool16, bool32 ("true"/"false")
Character	char, char8, char16, char32
Library	String, StringBuilder

Because of these, values like 42, true, and 'x' can be passed straight to Print and Format without manual conversion.

See also

• Format — build a String from a format string and Display arguments
• Print / PrintLine — write Display values to standard output