nuntius wrote:Outside of a computer, parens don't matter.
I'm not sure I agree with this. If I wish to communicate the form of expressions, it seems to me I should show how they are delimited. Boxes and underbars are awkward, and indenting can get all too easily sloppy. Imagine you're showing someone Gabriel's Why of Y
derivation, and you have only paper and pencil. It's all too easy to write expressions that aren't well formed. If you're explaining stuff at the same time, you're already walking and chewing gum.
Since my principal experience of lisp comes from reading code on line and in books, I've never seen subscripted parens used, so this is a new thought to me.
nuntius wrote:Do you need a computer representation of this, or are you just looking for ideas?
If a computer were involved, I wouldn't worry about a shorthand for paper or the whiteboard. What I'm interested in is considering a hand written notation for well formed
s-exprs without paren counting. Good notation is a significant part of the battle whether for pedagogic or nmemonic purposes. I am also interested in exploring a possible explanation of why beginners often cite the parens as a reason to detest lisp.