Pretty cool, some basic documentation would be nice (the readme does not tell everything). I didn't find how to reproduce some of the behavior of the loan example in the GIF, like how to format cells (turns out formatting is just writing a function that transforms a value and assigning it to the cell's 'f' field. Are there other special fields ?). I can't seem to make sub-table creation work, after creating a table with ctrl-alt-t, I seem to be stuck in table edition mode, I can't click on another cell or press enter or tab to deselect a cell.

I think it's a pretty promising project. Spreadsheets are very useful tools but usually crippled by single-line, crappy, not syntax-checking, not highlighting function editors.