75 lines
1.9 KiB
Ruby
75 lines
1.9 KiB
Ruby
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module UnitConversion
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class NumberFormatter
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def self.for(parsed_value, parsed_unit)
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case
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when parsed_unit && parsed_unit.metric?
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DecimalFormatter
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when parsed_value.rational?
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RationalFormatter
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else
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DecimalFormatter
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end.new
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end
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def initialize
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end
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# Converts a Numeric into a cooking-friendly Rational
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def rationalize(value)
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# NOTE: this algorithm seems stupid.
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if value.floor == value
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return value
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end
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useful_denominators = [2, 3, 4, 8, 16]
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if value.is_a?(Rational) && useful_denominators.include?(value.denominator)
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return value
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end
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whole = value.floor
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fraction = value - whole
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approximations = useful_denominators.map do |d|
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best_n = (1...d).each.map { |n| {delta: (fraction - Rational(n, d)).abs, numerator: n} }.sort { |a, b| a[:delta] <=> b[:delta] }.first
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{denominator: d, numerator: best_n[:numerator], delta: best_n[:delta]}
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end
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# Add 0 and 1
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approximations << { denominator: 1, numerator: 0, delta: (fraction - Rational(0,1)).abs }
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approximations << { denominator: 1, numerator: 1, delta: (fraction - Rational(1,1)).abs }
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best = approximations.sort { |a, b| [a[:delta], a[:denominator]] <=> [b[:delta], b[:denominator]] }.first
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Rational((whole * best[:denominator]) + best[:numerator], best[:denominator])
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end
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end
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class RationalFormatter < NumberFormatter
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def format(value)
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rational_val = rationalize(value)
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if rational_val.denominator == 1
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rational_val.to_i.to_s
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elsif rational_val.denominator < rational_val.numerator.abs
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whole = rational_val.floor
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fraction = rational_val - whole
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"#{whole} #{fraction}"
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else
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rational_val.to_s
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end
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end
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end
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class DecimalFormatter < NumberFormatter
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def format(value)
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"%g" % ("%.3f" % value)
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end
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end
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end
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