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Fundamental data types and type constructors, like Single, Pair, Many.

Module :: type_constructor

experimental rust-status docs.rs discord

Fundamental data types and type constructors, like Single, Pair, Homopair, Many.

In Rust, you often need to wrap a given type into a new one. The role of the orphan rules in particular is basically to prevent you from implementing external traits for external types. To overcome the restriction developer usually wrap the external type into a tuple introducing a new type. Type constructor does exactly that and auto-implement traits From, Into, Deref and few more for the constructed type.

Besides type constructor for single element there are type constructors for pair, homopair and many:

  • Single to wrap single element.
  • Pair to wrap pair of distinct elements.
  • HomoPair to wrap pair of elements with the same type.
  • Many to wrap Vec of elements.

Macro types for type constructing

The same macro types is responsible for generating code for Single, Pair, Homopair, Many. Each type constructor has its own keyword for that, but Pair and Homopair use the same keyword difference in a number of constituent types. It is possible to define all types at once.

#[ cfg( feature = "types" ) ]
{
  use type_constructor::prelude::*;

  types!
  {

    single MySingle : f32;
    single SingleWithParametrized : std::sync::Arc< T : Copy >;
    single SingleWithParameter : < T >;

    pair MyPair : f32;
    pair PairWithParametrized : std::sync::Arc< T1 : Copy >, std::sync::Arc< T2 : Copy >;
    pair PairWithParameter : < T1, T2 >;

    pair MyHomoPair : f32;
    pair HomoPairWithParametrized : std::sync::Arc< T : Copy >;
    pair HomoPairWithParameter : < T >;

    many MyMany : f32;
    many ManyWithParametrized : std::sync::Arc< T : Copy >;
    many ManyWithParameter : < T >;

  }
}

It generates more than 1000 lines of code, which otherwise you would have to write manually.

Without macro

Macro types is exposed to generate new types, but in some cases, it is enough to reuse already generated types of such kind. The library ships such types: Single, Pair, Homopair, Many. Note: If you avoid generating new types you will get in a position to be not able to define your own implementation of foreign traits because of orphan rule.


let i32_in_tuple = type_constructor::Single::< i32 >::from( 13 );
dbg!( i32_in_tuple );
// i32_in_tuple = Single( 13 )
let i32_and_f32_in_tuple = type_constructor::Pair::< i32, f32 >::from( ( 13, 13.0 ) );
dbg!( i32_and_f32_in_tuple );
// vec_of_i32_in_tuple = Pair( 13, 13.0 )
let two_i32_in_tuple = type_constructor::HomoPair::< i32 >::from( ( 13, 31 ) );
dbg!( two_i32_in_tuple );
// vec_of_i32_in_tuple = HomoPair( 13, 31 )
let vec_of_i32_in_tuple = type_constructor::Many::< i32 >::from( [ 1, 2, 3 ] );
dbg!( vec_of_i32_in_tuple );
// vec_of_i32_in_tuple = Many([ 1, 2, 3 ])

Make.

Make is the variadic constructor. It’s the unified interface of the arbitrary-length constructor. After implementing several traits Make0, Make1 up to MakeN one can use make make! to construct instances.

ⓘ
#[ cfg( feature = "make" ) ]
{
  use type_constructor::prelude::*;

  let instance1 : Struct1 = make!();
  let instance2 : Struct1 = make!( 13 );
  let instance3 : Struct1 = make!( 1, 3 );

}

Sample :: single-line single.

To define your own single-use macro types!. The single-line definition looks like that.

use type_constructor::prelude::*;
types!( single MySingle : i32 );
let x = MySingle( 13 );
println!( "x : {}", x.0 );

It generates code:

use type_constructor::prelude::*;

pub struct MySingle( pub i32 );

impl core::ops::Deref for MySingle
{
  type Target = i32;
  fn deref( &self ) -> &Self::Target
  {
    &self.0
  }
}
impl From< i32 > for MySingle
{
  fn from( src : i32 ) -> Self
  {
    Self( src )
  }
}
impl From< MySingle > for i32
{
  fn from( src : MySingle ) -> Self
  {
    src.0
  }
}

let x = MySingle( 13 );
println!( "x : {}", x.0 );

Sample :: single with derives and attributes.

It’s possible to define attributes as well as derives.

use type_constructor::prelude::*;
types!
{
  /// This is also attribute and macro understands it.
  #[ derive( Debug ) ]
  single MySingle : i32;
}
let x = MySingle( 13 );
dbg!( x );

It generates code:

use type_constructor::prelude::*;

/// This is also an attribute and macro understands it.
#[ derive( Debug ) ]
pub struct MySingle( pub i32 );

impl core::ops::Deref for MySingle
{
  type Target = i32;
  fn deref( &self ) -> &Self::Target
  {
    &self.0
  }
}
impl From< i32 > for MySingle
{
  fn from( src : i32 ) -> Self
  {
    Self( src )
  }
}
impl From< MySingle > for i32
{
  fn from( src : MySingle ) -> Self
  {
    src.0
  }
}

let x = MySingle( 13 );
dbg!( x );

Sample :: single with struct instead of macro.

Sometimes it’s sufficient to use a common type instead of defining a brand new one. You may use parameterized struct Single< T > instead of macro types! if that is the case.

use type_constructor::prelude::*;
let x = Single::< i32 >( 13 );
dbg!( x );

Sample :: single with a parametrized element.

Element of tuple could be parametrized.

use type_constructor::prelude::*;
types!
{
  #[ derive( Debug ) ]
  single MySingle : std::sync::Arc< T : Copy >;
}
let x = MySingle( std::sync::Arc::new( 13 ) );
dbg!( x );

It generates code:

use type_constructor::*;

#[ derive( Debug ) ]
pub struct MySingle< T : Copy >( pub std::sync::Arc< T > );

impl<T: Copy> core::ops::Deref for MySingle< T >
{
  type Target = std::sync::Arc< T >;
  fn deref( &self ) -> &Self::Target
  {
    &self.0
  }
}
impl< T : Copy > From< std::sync::Arc< T > > for MySingle< T >
{
  fn from( src : std::sync::Arc<T>) -> Self {
    Self( src )
  }
}
impl< T : Copy > From< MySingle< T > > for std::sync::Arc< T >
{
  fn from(src: MySingle<T>) -> Self
  {
    src.0
  }
}

let x = MySingle( std::sync::Arc::new( 13 ) );

Sample :: single with parametrized tuple.

Instead of parametrizing the element, it’s possible to define a parametrized tuple.

use type_constructor::prelude::*;
types!
{
  #[ derive( Debug ) ]
  single MySingle : < T : Copy >;
}
let x = MySingle( 13 );
dbg!( x );

It gererates code:

#[ derive( Debug ) ]
pub struct MySingle< T : Copy >( pub T );

impl< T : Copy > core::ops::Deref
for MySingle< T >
{
  type Target = T;
  fn deref( &self ) -> &Self::Target
  {
    &self.0
  }
}

impl< T : Copy > From< T >
for MySingle< T >
{
  fn from( src : T ) -> Self
  {
    Self( src )
  }
}

let x = MySingle( 13 );
dbg!( 13 );

Sample :: single-line pair

Sometimes you need to wrap more than a single element into a tupдe. If types of elements are different use pair. The same macro types is responsible for generating code for both single, pair and also many.

use type_constructor::prelude::*;

types!( pair MyPair : i32, i64 );
let x = MyPair( 13, 31 );
println!( "x : ( {}, {} )", x.0, x.1 );
// prints : x : ( 13, 31 )

It generates code:

Sample :: pair with parameters

Just like single pair may have parameters.

use type_constructor::prelude::*;

use core::fmt;
types!
{
  #[ derive( Debug ) ]
  pair MyPair : < T1 : fmt::Debug, T2 : fmt::Debug >;
}
let x = MyPair( 13, 13.0 );
dbg!( x );
// prints : x = MyPair( 13, 13.0 )

It generates code:

use type_constructor::prelude::*;
use core::fmt;

pub struct MyPair< T1 : fmt::Debug, T2 : fmt::Debug >( pub T1, pub T2 );

#[ automatically_derived ]
#[ allow( unused_qualifications ) ]
impl< T1 : ::core::fmt::Debug + fmt::Debug, T2 : ::core::fmt::Debug + fmt::Debug > ::core::fmt::Debug for MyPair< T1, T2 >
{
  fn fmt( &self, f : &mut ::core::fmt::Formatter ) -> ::core::fmt::Result
  {
    match *self
    {
      MyPair( ref __self_0_0, ref __self_0_1 ) =>
      {
        let debug_trait_builder = &mut ::core::fmt::Formatter::debug_tuple( f, "MyPair" );
        let _ = ::core::fmt::DebugTuple::field( debug_trait_builder, &&( *__self_0_0 ) );
        let _ = ::core::fmt::DebugTuple::field( debug_trait_builder, &&( *__self_0_1 ) );
        ::core::fmt::DebugTuple::finish( debug_trait_builder )
      }
    }
  }
}

impl< T1 : fmt::Debug, T2 : fmt::Debug > From<( T1, T2 )> for MyPair< T1, T2 >
{
  fn from( src : ( T1, T2 ) ) -> Self { Self( src.0, src.1 ) }
}

impl< T1 : fmt::Debug, T2 : fmt::Debug > From< MyPair< T1, T2 > > for ( T1, T2 )
{
  fn from( src : MyPair< T1, T2 > ) -> Self { ( src.0, src.1 ) }
}

#[ cfg( feature = "make" ) ]
impl< T1 : fmt::Debug, T2 : fmt::Debug > Make0 for MyPair< T1, T2 >
where
  T1 : Default,
  T2 : Default,
{
  fn make_0() -> Self { Self( Default::default(), Default::default() ) }
}

#[ cfg( feature = "make" ) ]
impl< T1 : fmt::Debug, T2 : fmt::Debug > Make2< T1, T2 > for MyPair< T1, T2 >
{
  fn make_2( _0 : T1, _1 : T2 ) -> Self { Self( _0, _1 ) }
}

let x = MyPair( 13, 13.0 );
dbg!( x );
// prints : x = MyPair( 13, 13.0 )

Sample :: single-line homopair

If you need to wrap pair of elements with the same type use the type constructor pair. The same type constructor pair for both pair and homopair, difference in number of types in definition, homopair has only one, because both its element has the same type. The same macro types is responsible for generating code for both single, pair and also many.

use type_constructor::prelude::*;

types!( pair MyPair : i32, i64 );
let x = MyPair( 13, 31 );
println!( "x : ( {}, {} )", x.0, x.1 );
// prints : x : ( 13, 31 )

It gererates code:

use type_constructor::prelude::*;

pub struct MyPair( pub i32, pub i64 );

impl From< ( i32, i64 ) > for MyPair
{
  fn from( src : ( i32, i64 ) ) -> Self { Self( src.0, src.1 ) }
}

impl From< MyPair > for ( i32, i64 )
{
  fn from( src : MyPair ) -> Self { ( src.0, src.1 ) }
}

#[ cfg( feature = "make" ) ]
impl Make2< i32, i64 > for MyPair
{
  fn make_2( _0 : i32, _1 : i64 ) -> Self { Self( _0, _1 ) }
}

let x = MyPair( 13, 31 );
println!( "x : ( {}, {} )", x.0, x.1 );

Sample :: homopair with parameters

Unlike heteropair homopair has much more traits implemented for it. Among such are: clone_as_tuple, clone_as_array to clone it as either tuple or array, as_tuple, as_array, as_slice to reinterpret it as either tuple or array or slice, traits From/Into are implemented to convert it from/into tuple, array, slice, scalar.

use type_constructor::prelude::*;

use core::fmt;
types!
{
  #[ derive( Debug ) ]
  pair MyHomoPair : < T : fmt::Debug >;
}
let x = MyHomoPair( 13, 31 );
dbg!( &x );
// prints : &x = MyHomoPair( 13, 31 )
let clone_as_array : [ i32 ; 2 ] = x.clone_as_array();
dbg!( &clone_as_array );
// prints : &clone_as_array = [ 13, 31 ]
let clone_as_tuple : ( i32 , i32 ) = x.clone_as_tuple();
dbg!( &clone_as_tuple );
// prints : &clone_as_tuple = ( 13, 31 )

It gererates code:

Sample :: single-line many

Use type constructor many to wrap Vec in a tuple. Similar to single it has essential traits implemented for it.

use type_constructor::prelude::*;

types!( many MyMany : i32 );
let x = MyMany::from( [ 1, 2, 3 ] );
println!( "x : {:?}", x.0 );

It generates code:

Sample :: make - 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

Re-exports

pub use super::internal::_many;
pub use super::internal::_pair;
pub use super::internal::_single;
pub use super::internal::make;
pub use super::internal::_many;
pub use super::internal::_pair;
pub use super::internal::_single;
pub use super::internal::make;
pub use super::internal::_many;
pub use super::internal::_pair;
pub use super::internal::_single;
pub use super::internal::make;

Modules

exposed

Exposed namespace of the module.

make

Variadic constructor.

many

Type constructor of many.

orphan

Orphan namespace of the module.

pair

Type constructor of pair.

prelude

Prelude to use essentials: use my_module::prelude::*.

protected

Protected namespace of the module.

single

Type constructor of single.

traits

Generic traits.

types

Type constructors.

Macros

_many

Type constructor of many.

_pair

Pair type constructor.

_single

Type constructor of single.

make

Variadic constructor.

types

Type constructor to define tuple wrapping a given type.

Structs

HomoPair

Type constructor to wrap pair of the same type.

Many

Type constructor to wrap a another type into a tuple.

Pair

Type constructor to wrap two types into a tuple.

Single

Type constructor to wrap a another type into a tuple.

Traits

AsArray

Reinterpret as array.

AsSlice

Reinterpret as slice.

AsTuple

Reinterpret as tuple.

CloneAsArray

Clone as array.

CloneAsTuple

Clone as tuple.

Make0

Constructor without arguments.

Make1

Constructor with single argument.

Make2

Constructor with two arguments.

Make3

Constructor with three arguments.