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Merge pull request #744 from marcoarnulfo:fix/roman-forms-2-3

This commit is contained in:
Brandon Thomas 2026-10-12 23:49:10 -04:00
parent 70c84e20ba 9e28655a8a
commit 705543521e
1 changed files with 43 additions and 4 deletions
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47
crates/functions/src/math.rs
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@ -642,16 +642,18 @@ fn radians(a: &[Arg], _c: &mut dyn Ctx) -> R<Value> {
const NUMERALS: [(char, u32); 7] = [('I', 1), ('V', 5), ('X', 10), ('L', 50), ('C', 100), ('D', 500), ('M', 1000)];
/// Tokens (text, value) for a ROMAN form, largest value first. Form 0 is classic; higher forms
/// allow subtracting progressively smaller numerals (max ratio 10, 20, 50, 100, 1000).
/// Tokens (text, value) for a ROMAN form, largest value first. Form 0 is classic; each higher
/// form widens one of two limits on the subtracted numeral's ratio to the larger one, alternating:
/// the limit for I/X/C (10, 10, 100, 100, 1000) and for V/L (none, 20, 20, 200, 200). So form 2
/// allows IC and XM but not VD, and form 3 adds VD and VM but not ID.
fn roman_tokens(form: u32) -> Vec<(String, u32)> {
let max_ratio = [10, 20, 50, 100, 1000].get(form as usize).copied().unwrap_or(10);
let (pow10_max, five_max) = [(10, 0), (10, 20), (100, 20), (100, 200), (1000, 200)].get(form as usize).copied().unwrap_or((10, 0));
let mut toks: Vec<(String, u32)> = NUMERALS.iter().map(|(c, v)| (c.to_string(), *v)).collect();
for (i, (sc, sv)) in NUMERALS.iter().enumerate() {
for (lc, lv) in NUMERALS.iter().skip(i + 1) {
let ratio = lv / sv;
let pow10 = matches!(sc, 'I' | 'X' | 'C');
let ok = if form == 0 { pow10 && ratio <= 10 } else { ratio <= max_ratio };
let ok = ratio <= if pow10 { pow10_max } else { five_max };
let value = lv - sv;
// Skip pairs that equal a single numeral (VX = V) – they are never shorter.
if ok && !NUMERALS.iter().any(|(_, v)| *v == value) {
@ -1572,6 +1574,43 @@ mod tests {
is_err(ev("DECIMAL", vec![t("12"), n(2.0)]), Num);
}
/// Every number where Excel's forms 2 and 3 differ from a plain ratio limit (issue #733):
/// form 2 subtracts I from C and X from M, form 3 also V from M.
#[test]
fn roman_forms_two_and_three_match_excel() {
const HUNDREDS: [&str; 10] = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"];
const ONES: [&str; 10] = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"];
let mut cases = Vec::new();
for thousands in 0..4usize {
let m = "M".repeat(thousands);
for (h, hundreds) in HUNDREDS.iter().enumerate() {
if h != 4 && h != 9 {
cases.push((thousands * 1000 + h * 100 + 99, 2.0, format!("{m}{hundreds}IC")));
}
}
for (o, ones) in ONES.iter().enumerate() {
cases.push((thousands * 1000 + 990 + o, 2.0, format!("{m}XM{ones}")));
}
for (o, ones) in ONES.iter().enumerate().take(5) {
cases.push((thousands * 1000 + 995 + o, 3.0, format!("{m}VM{ones}")));
}
}
assert_eq!(cases.len(), 92);
for (number, form, want) in &cases {
is_text(ev2("ROMAN", *number as f64, *form), want);
}
// Neighbours that already matched: form 2 still has no VD or ID, form 3 no ID.
is_text(ev2("ROMAN", 495.0, 2.0), "XDV");
is_text(ev2("ROMAN", 495.0, 3.0), "VD");
is_text(ev2("ROMAN", 1499.0, 2.0), "MXDIX");
is_text(ev2("ROMAN", 999.0, 0.0), "CMXCIX");
is_text(ev2("ROMAN", 999.0, 1.0), "LMVLIV");
is_text(ev2("ROMAN", 999.0, 4.0), "IM");
is_text(ev2("ROMAN", 995.0, 4.0), "VM");
is_text(ev2("ROMAN", 99.0, 1.0), "VCIV");
is_text(ev2("ROMAN", 99.0, 4.0), "IC");
}
#[test]
fn matrices() {
let a = arr(vec![vec![nv(1.0), nv(2.0)], vec![nv(3.0), nv(4.0)]]);