[Online interpreter] [Examples]
Fir is a programming language that aims to bring high-level programming with expressive types and typeclasses to the masses.
Some notable features are:
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Statically typed:
- Algebraic data types (ADTs) and pattern matching
- Typeclasses (called traits)
- Higher-kinded types
- Anonymous polymorphic products (records) and sums (variants)
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Indentation sensitive syntax
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Compile-time monomorphisation
Runtime polymorphism is possible via trait objects. By default, polymorphic code is monomorphised at compile time.
This allows efficient memory layout in types like
Vec:Vec[I32]holds a memory with 32-bit integers, instead of a memory with pointers to boxed 32-bit integer objects.It also allows unboxing objects with immutable fields (such as
Option,Result), and multiple return values without allocation via records. -
Whole-program compilation
Type checking and desugaring is done in a modular way.
Any analyses for performance, and code generation, are done for the whole program.
This allows simple implementation of monomorphisation, and simple and efficient implementation of runtime polymorphism (when using trait objects).
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Coroutines
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Tail call elimination (explicit with a keyword)
We want Fir to be a productive programming language when you need static types, with modern tooling (compiler, language server, documentation generator, formatter, build system, all in one executable), syntax, a batteries-included approach to the standard libraries, and an expressive type system.
We want to bootstrap Fir as quickly as possible.
To that end, only features that will help writing the bootstrapping compiler should be added to the interpreter, such as the type checker.
Features that are not absolutely needed to run the bootstrapping compiler will be left to the bootstrapped compiler. For example, the interpreter does not need to have a garbage collector.
Initially the compiler will only generate Wasm. In the long term we should have native backends as well.