[omaranto]

There is already a well-developed shell with rich data structures and a fairly reasonable programming language: Microsoft's PowerShell. Sadly it is not a Unix shell. You're probably aware of it, but if not, check it out for design inspiration.

[xiaq]

Of course! PowerShell definitely has a lot of brilliant ideas. Sadly it is overenginnered and has quite some design mistakes. Nevertheless it has served as a great source of inspiration for me - I have actually gone through several PowerShell manuals before I started elvish.

[ygra]

As someone who loves PowerShell and uses it daily, may I ask for specifics for design mistakes and overengineering? You may also answer per mail if you want.

Don't get me wrong, I realise it has its flaws and warts, but for me, and comparing to cmd or bash I still think it's very, very much an improvement.

Off the top of my head actual mistakes (the sort that tends to bite many people) include handling of [ and ] in -Path arguments (necessitating -LiteralPath arguments in later versions), and the constant wondering whether something returns a scalar or an array (and an array of one element being unwrapped into a scalar automatically). During my time working on Pash I also noted a few weirdnesses on source code side, most recently and notably LanguagePrimitives.Convert which has a dependency on the currently-executing runspace (which is stored in a thread-local field).