Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.
use super::funejson::Value; ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::math_round_float::round_float; ← from math.round-float ^1.0.0 · built alongside by fune
use super::text_format_decimal::format_decimal; ← from text.format-decimal ^1.0.0 · built alongside by fune
// yocto to yotta, as d3-format writes them (micro is U+00B5).
const PREFIXES: [&str; 17] = ["y", "z", "a", "f", "p", "n", "\u{b5}", "m", "", "k", "M", "G", "T", "P", "E", "Z", "Y"];
const THOUSANDS: [f64; 9] = [1.0, 1e3, 1e6, 1e9, 1e12, 1e15, 1e18, 1e21, 1e24];
const TENS: [f64; 3] = [1.0, 10.0, 100.0];
fn scale_and_round(value: f64, group: i64, places: i64) -> (f64, i64) {
let scaled = if group >= 0 { value / THOUSANDS[group as usize] } else { value * THOUSANDS[(-group) as usize] };
if places < 0 {
let unit = TENS[(-places) as usize];
return (round_float(scaled / unit, 0) * unit, 0);
}
let p = if places > 12 { 12 } else { places };
(round_float(scaled, p), p)
}
/// A number with an SI prefix and `significant` significant digits, trailing
/// zeros dropped: 1200 is "1.2k", 0.0015 is "1.5m".
///
/// # Panics
/// Panics if `significant` is outside 1..=15 or the value is not finite.
pub fn format_si(value: f64, significant: i64) -> String {
if !(1..=15).contains(&significant) {
panic!("significant must be a whole number from 1 to 15, received {}", significant);
}
if !value.is_finite() {
panic!("value must be a finite number, received {}", value);
}
if value == 0.0 {
return "0".to_string();
}
let a = value.abs();
let mut exponent: i64 = 0;
if a >= 1.0 {
let mut p = 1.0;
while p * 10.0 <= a {
p *= 10.0;
exponent += 1;
}
} else {
let mut q = 1.0;
while a * q < 1.0 {
q *= 10.0;
exponent -= 1;
}
}
let group = exponent.div_euclid(3).clamp(-8, 8);
let (mut rounded, mut places) = scale_and_round(value, group, significant - 1 - (exponent - 3 * group));
let mut group = group;
if rounded.abs() >= 1000.0 && group < 8 {
group += 1;
let next = scale_and_round(value, group, significant - 1);
rounded = next.0;
places = next.1;
}
format!("{}{}", format_decimal(rounded, places, true, ""), PREFIXES[(group + 8) as usize])
}
pub fn fune_vector(args: &[Value]) -> Value {
Value::str(&format_si(args[0].as_f64(), args[1].as_i64()))
}