Named measures

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Measurement units, using countries as example: population returns Reality::Measure[123400 people], which is inspectable and convertible, but checks unit on operations.

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Ideal requirements:

# Commons
# unit control
Measure[1, 'm'] + Measure[2, 'm'] # => Measure[3 m]
Measure[1, 'm'] + Measure[2, 's'] # => ConversionError
Measure[1, 'm'] * 3 # => Measure[3 m]

# symbolic computations
Measure[1, 'm'] / Measure[2, 's'] # => Measure[0.5 m/s]
Measure[1, 'm'] * Measure[3, 'm'] # => Measure[3 m²]
Measure[2, 'foo'] * Measure[3, 'foo'] / Measure[6, 'bar'] # => Measure[1 foo²/bar]

# pretty ouput (see above, all those "1 foo²/bar")

# Physical units
# unit conversion:
Measure[1, 'km'] + Measure[100, 'm'] # => Measure[1.1 km] or Measure[1100 m], don't know
Measure[1000, 'l'] / Measure[1, 'm'] # => Measure[1000 m²]

# ?interaction with Ruby's standard clasess:
Measure[1, 'hour'].since(Time.now) # => 1 hour in future

# ?but without core_ext'ing
Time.now + Measure[1, 'hour'] # => fails

Important: should work with any units (or be extendible, at least).

External candidates:

• https://github.com/joshwlewis/unitwise (cool conversions, only predefined units)
• https://github.com/masa16/phys-units (lot less cool than Unitwise, but link to GNU Units)

Currently it seems Unitwise is cool enough to try to extend it somehow?.. Or fork.

[zverok]

Partially implemented, see also #11 and #12