[m-messer]

Ports the number-string half of compareExpressions#273 and #277 (sig_figs / decimal_places) to expression_parsing. The grading (sig_figs_match, decimal_places_match, the tolerances) and the feedback stay in compareExpressions.

expression_parsing

• read_written_number(string) returns a WrittenNumber (integer, fraction, has_point, exponent), or None if string isn't exactly one decimal number.
• .significant_figures skips leading zeros. It counts trailing zeros only after a written point: 540 has 2, 540. has 3, and 92.00 has 4.
• .decimal_places subtracts the exponent: 5.02e4 has 0, and 5e-3 has 3.
• It's more lenient than is_number, because it reads what a learner wrote: a + sign, leading zeros and a trailing point are accepted. The exponent can be written e, E, *10^ or *10**; #273/#277 only read e/E.
• round_to_significant_figures(value, figures) returns a float.
• round_to_decimal_places(value, places) returns a string that keeps its trailing zeros.

Verification

• ruff, format and mypy are clean. The package tests pass (tests/test_written_number.py is new), and so does the parity check.

🤖 Generated with Claude Code