CAS command question

[DrD]

part(Expr, Integer) isn't a viable replacement. It requires advance awareness of the nth number of sub-expressions, an extra handling process.

The discussion isn't about finding a way to accomplish this task. There are a variety of ways the CONCEPT of left() or right() "COULD" be made to work. Unfortunately, it seems there isn't a 'single' command, that simply returns it's namesake, without complication; hence the whole point of this discussion.

It might be better to start a new topic on the consequences of evaluation first, or of single quoting expressions, etc., if you would care to pursue the alternatives.