Macro std_tools::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.

#[ cfg( feature = "make" ) ]
{
  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