Module chars_util 

Character helpers shared by the structural matchers. The reference walks Python strings by code point; these helpers provide the same semantics over Rust byte offsets.

Functions

char_at

The character starting at (or spanning) byte_idx, if the index is a char boundary.

char_before

The character ending just before byte_idx, if byte_idx is a boundary.

py_is_word

Python \w membership (Unicode word character or underscore).

str_find_from

Python str.find(sub, start, end).

str_rfind_in

Python str.rfind(sub, start, end): last occurrence within [start, end).

walk_back_while

Walk to the start of the run of pred characters ending at byte_idx (exclusive), like the reference’s backward while loops.

walk_forward_while

Walk forward from byte_idx over pred characters, returning the end.