Length.toMm for Cm

Every physical Length stores a signed 64-bit scaled-point count and a unit marker. The inclusive count range is -9223372036854775808 through 9223372036854775807. Zero and negative lengths are valid.

One point is 65,536 scaled points. One inch is 72 points and exactly 25.4 millimetres. One centimetre is 10 millimetres.

A physical literal converts its exact decimal value to scaled points and rounds once to the nearest integer. An exact tie selects the even integer. The same rule applies to either sign.

The methods toPt, toMm, toCm, and toIn accept no arguments on Length<Pt>, Length<Mm>, Length<Cm>, and Length<In>. They return the named physical unit with the original scaled-point count.

A unit conversion performs no further rounding and cannot overflow. Converting to the existing unit returns the same typed value. Every conversion sequence preserves the physical distance and stored count.

The unit marker remains part of the static type. Assignment and function arguments do not convert units implicitly. A required Length<Pt> rejects another unit with TPZ5001. Convert explicitly before the call or assignment.

Length<Em> has no physical conversion member. Resolve it with an explicit positive point font size before converting units.

Each method evaluates its receiver once before producing the result. Conversion performs no I/O or mutation and reads no font or paragraph state.

Use toScaledPoints on any physical unit for the exact stored integer. Convert to Length<Pt> before calling toMilliPoints. The integer conversion contract defines its separate rounding boundary.