diff options
Diffstat (limited to 'tvix/eval/src/value/mod.rs')
| -rw-r--r-- | tvix/eval/src/value/mod.rs | 146 |
1 files changed, 75 insertions, 71 deletions
diff --git a/tvix/eval/src/value/mod.rs b/tvix/eval/src/value/mod.rs index f9ada2b627b5..12b3592e1625 100644 --- a/tvix/eval/src/value/mod.rs +++ b/tvix/eval/src/value/mod.rs @@ -514,6 +514,80 @@ impl Display for Value { } } +/// Emulates the C++-Nix style formatting of floats, which diverges +/// significantly from Rust's native float formatting. +fn total_fmt_float<F: std::fmt::Write>(num: f64, mut f: F) -> std::fmt::Result { + let mut buf = [b'0'; lexical_core::BUFFER_SIZE]; + let mut s = lexical_core::write_with_options::<f64, { CXX_LITERAL }>( + num.clone(), + &mut buf, + &WRITE_FLOAT_OPTIONS, + ); + + // apply some postprocessing on the buffer. If scientific + // notation is used (we see an `e`), and the next character is + // a digit, add the missing `+` sign.) + let mut new_s = Vec::with_capacity(s.len()); + + if s.contains(&b'e') { + for (i, c) in s.iter().enumerate() { + // encountered `e` + if c == &b'e' { + // next character is a digit (so no negative exponent) + if s.len() > i && s[i + 1].is_ascii_digit() { + // copy everything from the start up to (including) the e + new_s.extend_from_slice(&s[0..=i]); + // add the missing '+' + new_s.push(b'+'); + // check for the remaining characters. + // If it's only one, we need to prepend a trailing zero + if s.len() == i + 2 { + new_s.push(b'0'); + } + new_s.extend_from_slice(&s[i + 1..]); + break; + } + } + } + + // if we modified the scientific notation, flip the reference + if new_s.len() != 0 { + s = &mut new_s + } + } + // else, if this is not scientific notation, and there's a + // decimal point, make sure we really drop trailing zeroes. + // In some cases, lexical_core doesn't. + else if s.contains(&b'.') { + for (i, c) in s.iter().enumerate() { + // at `.`` + if c == &b'.' { + // trim zeroes from the right side. + let frac = String::from_utf8_lossy(&s[i + 1..]); + let frac_no_trailing_zeroes = frac.trim_end_matches("0"); + + if frac.len() != frac_no_trailing_zeroes.len() { + // we managed to strip something, construct new_s + if frac_no_trailing_zeroes.is_empty() { + // if frac_no_trailing_zeroes is empty, the fractional part was all zeroes, so we can drop the decimal point as well + new_s.extend_from_slice(&s[0..=i - 1]); + } else { + // else, assemble the rest of the string + new_s.extend_from_slice(&s[0..=i]); + new_s.extend_from_slice(frac_no_trailing_zeroes.as_bytes()); + } + + // flip the reference + s = &mut new_s; + break; + } + } + } + } + + write!(f, "{}", format!("{}", String::from_utf8_lossy(&s))) +} + impl TotalDisplay for Value { fn total_fmt(&self, f: &mut std::fmt::Formatter<'_>, set: &mut ThunkSet) -> std::fmt::Result { match self { @@ -531,77 +605,7 @@ impl TotalDisplay for Value { // Nix prints floats with a maximum precision of 5 digits // only. Except when it decides to use scientific notation // (with a + after the `e`, and zero-padded to 0 digits) - Value::Float(num) => { - let mut buf = [b'0'; lexical_core::BUFFER_SIZE]; - let mut s = lexical_core::write_with_options::<f64, { CXX_LITERAL }>( - num.clone(), - &mut buf, - &WRITE_FLOAT_OPTIONS, - ); - - // apply some postprocessing on the buffer. If scientific - // notation is used (we see an `e`), and the next character is - // a digit, add the missing `+` sign.) - let mut new_s = Vec::with_capacity(s.len()); - - if s.contains(&b'e') { - for (i, c) in s.iter().enumerate() { - // encountered `e` - if c == &b'e' { - // next character is a digit (so no negative exponent) - if s.len() > i && s[i + 1].is_ascii_digit() { - // copy everything from the start up to (including) the e - new_s.extend_from_slice(&s[0..=i]); - // add the missing '+' - new_s.push(b'+'); - // check for the remaining characters. - // If it's only one, we need to prepend a trailing zero - if s.len() == i + 2 { - new_s.push(b'0'); - } - new_s.extend_from_slice(&s[i + 1..]); - break; - } - } - } - - // if we modified the scientific notation, flip the reference - if new_s.len() != 0 { - s = &mut new_s - } - } - // else, if this is not scientific notation, and there's a - // decimal point, make sure we really drop trailing zeroes. - // In some cases, lexical_core doesn't. - else if s.contains(&b'.') { - for (i, c) in s.iter().enumerate() { - // at `.`` - if c == &b'.' { - // trim zeroes from the right side. - let frac = String::from_utf8_lossy(&s[i + 1..]); - let frac_no_trailing_zeroes = frac.trim_end_matches("0"); - - if frac.len() != frac_no_trailing_zeroes.len() { - // we managed to strip something, construct new_s - if frac_no_trailing_zeroes.is_empty() { - // if frac_no_trailing_zeroes is empty, the fractional part was all zeroes, so we can drop the decimal point as well - new_s.extend_from_slice(&s[0..=i - 1]); - } else { - // else, assemble the rest of the string - new_s.extend_from_slice(&s[0..=i]); - new_s.extend_from_slice(frac_no_trailing_zeroes.as_bytes()); - } - - // flip the reference - s = &mut new_s; - break; - } - } - } - } - - write!(f, "{}", format!("{}", String::from_utf8_lossy(&s))) - } + Value::Float(num) => total_fmt_float(*num, f), // internal types Value::AttrNotFound => f.write_str("internal[not found]"), |