Rust is great, but this is an important comment! We used it to implement Weld's compiler and runtime, but we don't expect data scientists who use languages such as Python, Julia, or R to switch over to it; the idea is that these data scientists continue using APIs in these languages, and under the hood, Weld will perform optimizations and compilation for decreasing execution time (and these "under the hood" components are the ones that we wrote in Rust).