Length Unit Converter
- Support various Length Unit Conversion:

- Support 1. Metric -> Metric:
i) Mode1:
[kilometre, metre, decimetre, centimetre, millimetre, micrometre, nanometre, Angstrom] -> [kilometre, metre, decimetre, centimetre, millimetre, micrometre, nanometre, Angstrom]
ii) Mode2: [km, m, dm, cm, mm, um, nm, Å] -> [km, m, dm, cm, mm, um, nm, Å]

- Support 2. Metric -> Imperial:
i) Mode1:
[kilometre, metre, decimetre, centimetre, millimetre, micrometre, nanometre, Angstrom] -> [league, mile, furlong, chain, rod, yard, fathom, foot, link, hand, inch, line, mil, thou]
ii) Mode2: [km, m, dm, cm, mm, um, nm, Å] -> [league, mi, furlong, chain, rd, yd, fathom, foot, link, hand, inch, line, mil, thou]

- Support 3. Imperial -> Imperial:
i) Mode1:
[league, mile, furlong, chain, rod, yard, fathom, foot, link, hand, inch, line, mil, thou] -> [league, mile, furlong, chain, rod, yard, fathom, foot, link, hand, inch, line, mil, thou]
ii) Mode2: [league, mi, furlong, chain, rd, yd, fathom, foot, link, hand, inch, line, mil, thou] -> [league, mi, furlong, chain, rd, yd, fathom, foot, link, hand, inch, line, mil, thou]

- Support 4. Imperial -> Metric:
i) Mode1:
[league, mile, furlong, chain, rod, yard, fathom, foot, link, hand, inch, line, mil, thou] -> [kilometre, metre, decimetre, centimetre, millimetre, micrometre, nanometre, Angstrom]
ii) Mode2: [league, mi, furlong, chain, rd, yd, fathom, foot, link, hand, inch, line, mil, thou] -> [km, m, dm, cm, mm, um, nm, Å]

- Fast calculation ~~

- High Precision: (1) 99% cases have > 11 decimal places for "infinite" decimal number.
(2) precise decimal value for "finite" decimal number.

- Suitable for works / homework / learning unit purposes.