When the point is not at the beginning of a word/sexp,
backward-word / backward-sexp places the cursor at the beginning of that word/sexp. If the point is already at the beginning of a word/sexp, this is of course not the case.
How to go to the beginning of the current word/sexp regardless of the point position?
Edit 1: By current sexp, I mean the smallest sexp containing the point, for example if the cursor is at
o in the expression
(end-of-line), the current sexp would be
end-of-line. If the cursor is at
(, the current sexp would be the whole
Edit 2: Another reformulation of this question: how to detect if the point is at the beginning of the current word/sexp?