Function format_float

src/repr/src/strconv.rs:290–330

(buf: &mut F, f: Fl)

}

fn format_float<F, Fl>(buf: &mut F, f: Fl) -> Nestable
where
    F: FormatBuffer,
    Fl: NumFloat + RyuFloat,
{
    // Use ryu rather than the standard library. ryu uses scientific notation
    // when possible, which better matches PostgreSQL. The standard library's
    // `ToString` implementations print all available digits, which is rather
    // verbose.
    //
    // Note that we have to fix up ryu's formatting in a few cases to match
    // PostgreSQL. PostgreSQL spells out "Infinity" in full, never emits a
    // trailing ".0", formats positive exponents as e.g. "1e+10" rather than
    // "1e10", and emits a negative sign for negative zero. If we need to speed
    // up float formatting, we can look into forking ryu and making these edits
    // directly, but for now it doesn't seem worth it.

    match f.classify() {
        FpCategory::Infinite if f.is_sign_negative() => buf.write_str("-Infinity"),
        FpCategory::Infinite => buf.write_str("Infinity"),
        FpCategory::Nan => buf.write_str("NaN"),
        FpCategory::Zero if f.is_sign_negative() => buf.write_str("-0"),
        _ => {
            debug_assert!(f.is_finite());
            let mut ryu_buf = ryu::Buffer::new();
            let mut s = ryu_buf.format_finite(f);
            if let Some(trimmed) = s.strip_suffix(".0") {
                s = trimmed;
            }
            let mut chars = s.chars().peekable();
            while let Some(ch) = chars.next() {
                buf.write_char(ch);
                if ch == 'e' && chars.peek() != Some(&'-') {
                    buf.write_char('+');
                }
            }
        }
    }

    Nestable::Yes
}

/// Parses an `f32` from `s`.
pub fn parse_float32(s: &str) -> Result<f32, ParseError> {