I wanted to play around with designing a new programming language and was reminded how much I value F# for this. F# - Its powerful data modeling coupled with its ability to interface with modern platforms (my language will run on the GPU), backed by a powerful runtime, combined with its excellent FsLex/Yacc makes it unrivaled. 1. JavaScript - nice for getting a cross-platform UI up, but the language is not good for modeling and experimenting. 2. TypeScript - better modeling than JS but no REPL 3. C# - Only supports OOP modeling and is a little verbose for fun prototyping. 4. C++ - Spend more time working on build scripts and dependency management that prototyping is no fun. 5. Python - Great development environment but terrible language for data modeling. 6. Swift - OKish modelling (so long as you can work around their memory manager limitations) but immature parsing ecosystems and I, personally, feel like my code in trapped forever by Xcode and Apple's whims.