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ROUND: keep 15 significant digits when asked for 15+ digits, so ROUND(0.1+0.2,15) is 0.3 (#58)

This commit is contained in:
MarekSpodBiedry 2026-10-09 19:29:29 +02:00
parent 51b531be3e
commit 2c2d92ef6b
1 changed files with 5 additions and 1 deletions
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6
crates/functions/src/util.rs
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@ -235,7 +235,9 @@ pub(crate) fn round_half_away(x: f64, digits: i32) -> f64 {
// value = 0.d1d2…d15 × 10^(e+1); keep the first `keep` digits.
let keep = e + 1 + digits;
if keep >= d.len() as i64 {
return x;
// Nothing to round off, but Excel still keeps only 15 significant digits, which drops binary noise
// such as 0.1 + 0.2 = 0.30000000000000004.
return to_sig_digits(x, d.len());
}
if keep < 0 {
return 0.0;
@ -416,6 +418,8 @@ mod tests {
assert_eq!(round_half_away(1234.5678, -2), 1200.0);
assert_eq!(round_half_away(0.285, 2), 0.29);
assert_eq!(round_half_away(1.005, 2), 1.01);
assert_eq!(round_half_away(0.1 + 0.2, 15), 0.3);
assert_eq!(round_half_away(0.1 + 0.2, 20), 0.3);
}
#[test]