String Conversion with ard/string

The ard/string module defines the ToString trait, which allows custom types to be converted to strings. This trait is fundamental to Ard’s type system and is used throughout the standard library.

The string module provides:

ToString trait for implementing custom string conversion
Integration with io::print and string interpolation

use ard/string as Str

struct Person {
  name: Str,
  age: Int
}

impl Str::ToString for Person {
  fn to_str() Str {
    "{@name} ({@age})"
  }
}

fn main() {
  let person = Person { name: "Alice", age: 30 }
  io::print(person)  // Uses to_str() automatically
}

API

`trait ToString`

A trait that types can implement to define how they should be converted to strings.

use ard/string as Str

trait ToString {
  fn to_str() Str
}

Implementing ToString

To implement ToString for a custom type, use the impl syntax:

use ard/string as Str

struct Point {
  x: Int,
  y: Int
}

impl Str::ToString for Point {
  fn to_str() Str {
    "({@x}, {@y})"
  }
}

Built-in Implementations

The following built-in types have to_str() methods:

Str: Returns itself
Int: Converts to decimal string representation
Float: Converts to decimal string representation
Bool: Returns “true” or “false”

Examples

Implement ToString for Enum

use ard/string as Str
use ard/io

enum Color {
  red,
  green,
  blue
}

impl Str::ToString for Color {
  fn to_str() Str {
    match @ {
      Color::red => "Red",
      Color::green => "Green",
      Color::blue => "Blue"
    }
  }
}

fn main() {
  let color = Color::red
  io::print(color)  // "Red"
}

Implement ToString for Struct

use ard/string as Str
use ard/io

struct Rectangle {
  width: Int,
  height: Int
}

impl Str::ToString for Rectangle {
  fn to_str() Str {
    "Rectangle {width: {@width}, height: {@height}}"
  }
}

fn main() {
  let rect = Rectangle { width: 10, height: 20 }
  io::print(rect)  // "Rectangle {width: 10, height: 20}"
}

Use in String Interpolation

use ard/string as Str
use ard/io

struct Date {
  year: Int,
  month: Int,
  day: Int
}

impl Str::ToString for Date {
  fn to_str() Str {
    "{@year}-{@month}-{@day}"
  }
}

fn main() {
  let today = Date { year: 2024, month: 1, day: 15 }
  io::print("Today is {today}")
}

Use with Functions

use ard/string as Str

fn print_value(val: Str::ToString) {
  io::print(val)
}

fn main() {
  print_value(42)
  print_value("hello")
  print_value(true)
}