> You can use Terra and Lua as…
> A scripting-language with high-performance extensions. While the performance of Lua and other dynamic languages is always getting better, a low-level of abstraction gives you predictable control of performance when you need it. Terra programs use the same LLVM backend that Apple uses for its C compilers. This means that Terra code performs similarly to equivalent C code. For instance, our translations of the nbody and fannhakunen programs from the programming language shootout1 perform within 5% of the speed of their C equivalents when compiled with Clang, LLVM’s C frontend. Terra also includes built-in support for SIMD operations, and other low-level features like non-temporal writes and prefetches. You can use Lua to organize and configure your application, and then call into Terra code when you need controllable performance.
> An embedded JIT-compiler for building languages. We use techniques from multi-stage programming to make it possible to meta-program Terra using Lua. Terra expressions, types, and functions are all first-class Lua values, making it possible to generate arbitrary programs at runtime. This allows you to compile domain-specific languages (DSLs) written in Lua into high-performance Terra code. Furthermore, since Terra is built on the Lua ecosystem, it is easy to embed Terra-Lua programs in other software as a library. This design allows you to add a JIT-compiler into your existing software. You can use it to add a JIT-compiled DSL to your application, or to auto-tune high-performance code dynamically.
> A stand-alone low-level language. Terra was designed so that it can run independently from Lua. In fact, if your final program doesn’t need Lua, you can save Terra code into a .o file or executable. In addition to ensuring a clean separation between high- and low-level code, this design lets you use Terra as a stand-alone low-level language. In this use-case, Lua serves as a powerful meta-programming language. You can think of it as a replacement for C++ template metaprogramming or C preprocessor X-Macros4 with better syntax and nicer properties such as hygiene. Since Terra exists only as code embedded in a Lua meta-program, features that are normally built into low-level languages can be implemented as Lua libraries. This design keeps the core of Terra simple, while enabling powerful behavior such as conditional compilation, namespaces, templating, and even class systems implemented as libraries.