FastLua is a Lua 5.2 implementation in pure C#, running on .NET 5.

There are already some popular Lua implementations in C#, including MoonSharp and KopiLua. However, I found these implementations too slow when I was testing ScriptBlazor.

Github Actions contains a benchmark that tracks the performance of FastLua compared with the other two implementations.

Q: So, how fast is it?
A: Currently 2-4 times faster than the other two implementations. Expect much more than this once the JIT (to CIL) is implemented.

Q: What kind of API does it expose?
A: It will not have similar API as original Lua implementation. This is mainly because it uses .NET GC, and the interop between C# and Lua is different from C. The API will be more C#-ish. For example, use custom awaitable for coroutines.

Q: Will it support older versions of the runtime?
A: No. It intensively uses new features such as ref return and Span. While it might be possible to run under .NET Standard 2.1, it won't be easy to make it run on older runtimes, including Unity.

Basic functionality:

• Call Lua from C#.
• Call C# from Lua.
• Metatable.
• Exception handling.
• Coroutine.

Optimizations:

• AST optimizations.
• Instruction specialization.
• JIT with System.Reflection.Emit.

Standard library:

• Basic.
• String.
• Table.
• Math.
• Bitwise.
• IO.
• OS.

Features that will not be supported:

• Modules library.
• Weak table (ephemeron is not supported by .NET).
• Lua Debug Interface.