Macro fundamental_data_type::make

macro_rules! make {
    (
      $(,)?
    ) => { ... };
    (
      $Arg1 : expr $(,)?
    ) => { ... };
    (
      $Arg1 : expr, $Arg2 : expr $(,)?
    ) => { ... };
    (
      $Arg1 : expr, $Arg2 : expr, $Arg3 : expr $(,)?
    ) => { ... };
    (
      $( $Rest : tt )+
    ) => { ... };
}

Variadic constructor.

Implement traits Make0, Make1 up to MakeN to provide the interface to construct your structure with a different set of arguments. In this example structure, Struct1 could be constructed either without arguments, with a single argument, or with two arguments.

• Constructor without arguments fills fields with zero.
• Constructor with a single argument sets both fields to the value of the argument.
• Constructor with 2 arguments set individual values of each field.

use type_constructor::prelude::*;

#[ derive( Debug, PartialEq ) ]
struct Struct1
{
  a : i32,
  b : i32,
}

impl Make0 for Struct1
{
  fn make_0() -> Self
  {
    Self { a : 0, b : 0 }
  }
}

impl Make1< i32 > for Struct1
{
  fn make_1( val : i32 ) -> Self
  {
    Self { a : val, b : val }
  }
}

impl Make2< i32, i32 > for Struct1
{
  fn make_2( val1 : i32, val2 : i32 ) -> Self
  {
    Self { a : val1, b : val2 }
  }
}

let got : Struct1 = make!();
let exp = Struct1{ a : 0, b : 0 };
assert_eq!( got, exp );

let got : Struct1 = make!( 13 );
let exp = Struct1{ a : 13, b : 13 };
assert_eq!( got, exp );

let got : Struct1 = make!( 1, 3 );
let exp = Struct1{ a : 1, b : 3 };
assert_eq!( got, exp );

To add to your project

cargo add type_constructor

Try out from the repository

git clone https://github.com/Wandalen/wTools
cd wTools
cd sample/rust/type_constructor_trivial_sample
cargo run