function editor

[cben]

The UX I had in mind is extremely similar to this thing I just found:
https://archive.org/details/akkartik-2min-2020-12-06

• language: support function definitions (no definition syntax, just given as name->string dictionary)
• support multiple editors, one per function
• when cursor stands on a function, embed an editor of the refenced function underneath it
• allow live editing of the embedded editor right there — this supports "example-driven" development, where to get useful feedback on function execution, you need to set up some params before calling it
• language: return a full execution trace
• when cursor travels inside an embedded editor, show stack at that point inside
• keybindings and/or buttons to single-step execution including nested functions