DurationFormatters

fn

pub const fn FormatTo<Rep, const Numerator: u64, const Denominator: u64>(
    Value: readonly Duration<Rep, Numerator, Denominator>&, Builder: mut StringBuilder&) -> void
    where Rep: Data, DurationCount, Formattable

Appends an exact duration count and its canonical reduced unit.

Count formatting composes the statically selected Formattable representation; it does not convert units, narrow counts or create an intermediate String. Known periods print a canonical suffix. Custom periods print (N/D s) so the per-count scale remains explicit. Borrowed inputs do not escape. Only Builder is mutated; callers synchronize its use and observe sticky allocation failure through checked finalization. Runtime builder growth may allocate. Rep: Copyable Defaultable count with a structural Formattable witness. Numerator: Positive compile-time seconds numerator. Denominator: Positive compile-time seconds denominator. Value: Readonly duration borrowed for this entire formatting call. Builder: Writable UTF-8 destination; mutation invalidates prior views. Return: No value; destination finalization reports sticky allocation failure.

Example

module example.duration_formatting;
from std.format import FormatTo;
from std.text import StringBuilder;
from std.time import Duration, Milliseconds, Years;
fn Main() -> i32 {
    var Builder = StringBuilder();
    FormatTo(Milliseconds.Create(2250), Builder);
    Builder.Append("; ");
    FormatTo(Years.Create(2), Builder);
    Builder.Append("; ");
    FormatTo(Duration<i64, 6, 4>.Create(7), Builder);
    switch Builder.TryFinalize() {
        case .Ok { Value = Text } => {
            if Text.View != "2250 ms; 2 years; 7 (3/2 s)" { return 1; }
        }
        case .Err => return 2;
    }
    return 0;
}