I have an idea for some system to get key choices auto-abbreviated and even a bit typo resilient (if the typo happens towards the end). I have not yet developed an implementation draft and don't know the performance, yet (the algorithm should be O(log n) at use time as it's basically some form of binary search -- but you never know for sure how well it behaves in TeX).
This would basically mean that for a list of valid choices `default, deprecated, foo, bar` any of the following input would work:
- `def` -> default
- `depercated` -> deprecated (anything at least starting with `dep` would do, so also `depault`)
- `f` -> foo
- `ba` -> bar
My basic plan would be to implement this fully expandable and hence I'd not be able to throw a warning that there was a choice substitution!
The basic layout would look like the following decision tree that'd be created while the choices are set up:
```
d
--------------|--------------
↓ ↓ ↓
b e f
-----|----- ----|---- -----|-----
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
ERR bar ERR ERR f ERR ERR foo ERR
-------|------
↓ ↓ ↓
ERR default p
--------|---------
↓ ↓ ↓
ERR deprecated ERR
```
You read it like this: Coming from the top if the current character in the input matches the tree node go straight down and move to the next input character, if it's charcode is smaller go below left, and if it's bigger go below right. Each node called `ERR` is an error message picking up any non-`ERR` leaf node of its parent as valid choices and generating an error message along the lines of "ambiguous input <input>, did you mean any of <list-of-leafs>?". Any multi-letter node is what I called a leaf node (a valid final result).
Do you think people would be interested in this?