User Defined Types

You can define your own data types in Graphix. This is useful for many tasks, such as enforcing interface invariants, and modeling data. As a data modeling language Graphix supports both structures, so called conjunctive types, where you are modeling data that always appears together, and variants, or so called disjunctive types, where a type can be one of many possible types drawn from a set. This contrasts with other languages, for example Python, which only support conjunctive types.

Structural Typing

In most languages types are dealt with by name, meaning that two structs with exactly the same fields are still different types if they have a different name. The obvious implication of this is that all types need to be given a name, and thus declared. Graphix works differently. Types in Graphix are structural, meaning that types that are structurally the same are the same type. In fact types in Graphix don't formally have names, there can be aliases for a large type to cut down on verbosity, but an alias is always resolved to the structural type when type checking. Because of this you don't need to declare types before using them.

Set Based Type System

The Graphix type system is based on set operations. For example, a function could declare that it can take either an i32 or an i64 as an argument by defining the set, [i32, i64] and annotating it's argument with this type.

let f = |a: [i32, i64]| ...

When this function is called, the type checker will check that the type of argument a is a subset of [i32, i64], and will produce a type error if it is not. Pretty much every operation the type checker performs in Graphix is one of, or a combination of, simple set operations contains, union, difference, etc.

The combination of structural typing, set based type operations, and aggressive type inference is meant to make Graphix feel like an untyped scripting language most of the time, but still catch a lot of mistakes at compile time, and make it possible to enforce interface contracts.