Crate typestates_comparison

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Comparison of different implementations of typestates.

There are three primary ways of implementing typestates:

  • individual types,
  • generic type with phantom types,
  • generic type with real types.

The last approach can also be implemented with the help of the typestate crate.

In this library we compare the three approaches by implementing the following system.

  • An entity gets created with an ID.
  • We can add a key a or b to the entity, but not both.
  • After we’ve added a or b, we can add c.
  • The entity is now ready to be used, i.e. printed.

Examples

Individual types

use typestates_comparison::individual_types::*;
let e = Initial::new(42);
let e = e.add_a(3.14);
let e = e.add_c('a');
assert_eq!(e.format(), format!("id:42 a:3.14 c:a"));

Generic type with phantom types

use typestates_comparison::phantom_types::*;
let e = Entity::new(42);
let e = e.add_a(3.14);
let e = e.add_c('a');
assert_eq!(e.format(), format!("id:42 a:3.14 c:a"));

Generic type with real types

use typestates_comparison::real_types::*;
let e = Entity::new(42);
let e = e.add_a(3.14);
let e = e.add_c('a');
assert_eq!(e.format(), format!("id:42 a:3.14 c:a"));

Generic type with real types (typestate crate)

use typestates_comparison::typestate_crate::*;
let e = Entity::new(42);
let e = e.add_a(3.14);
let e = e.add_c('a');
assert_eq!(e.format(), format!("id:42 a:3.14 c:a"));

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