Our implementation

How close our Rust is to Excel

This page states what we conclude about our own implementation of each entry, CalcFunc, from recorded Excel answers. It is regenerated from DnaCalc commit 9e1884369a67; nothing on it is typed by hand. CalcFunc has no repository of its own: it is the crate calc-func in DnaCalc/DnaCalc.

554 entries = 531 functions + 23 operators = 534 published Excel rows + 7 split byte-variant rows + 13 added functions.

What was compared

Two sources of recorded Excel answers. The answer bank holds 3,910,007 rows, of which 3,831,336 match; the workbook corpus holds 54,794 formula cells, of which 52,988 match. Every mismatch, refusal and pending cell stays a failure in those totals. A row or cell belongs to one function, the outermost call of its formula, and an operator is credited with formulas whose first operator it is, so a difference counted there can come from elsewhere in the formula. The two sources may overlap, so a function's count is the number of recorded answers compared, not the number of distinct calls.

A number matches only when all 64 bits of its binary64 value agree. The answer-bank counts were measured at revision 919dd43269b9 and committed in DnaCalc; calc-func has changed since that report landed, so the code shown may be newer than the counts. The corpus was run again at 9e1884369a67 for this page and gives the same totals. These statements cover the recorded inputs, Excel builds and platforms and nothing else. No Handbook test suite is published yet.

Last-bit: finite numeric mismatches <=16 ULP; larger numeric: >16 ULP. This split is triage, not a relaxed verdict. Every mismatch, refusal, unread, missing, pending, external and circular-policy cell remains an inclusive failure. Corpus labels follow exact single-cell aliases, infer calls from formula spelling and unwrap INDEX selections; unresolved references and infix operators remain explicit. Bank functions use canonical judge identities. Counts are observations per source; corpus and bank may overlap and must not be added as unique calls. Bank reference/locale context gaps remain failures, not proven numerical defects.