Class: Equalshares::Election

Inherits:
Object
  • Object
show all
Defined in:
lib/equalshares/election.rb

Overview

A numeric view of an instance for a given accuracy. It exposes the voters, projects and supporters together with the per-project cost, the budget and the per-voter utilities, all converted to the right numeric type (exact Rational for "fractions", Float for "floats"). This centralises the setup that every rule previously repeated, and provides the float-based statistics used for reporting.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(instance, params = Params.new) ⇒ Election

Returns a new instance of Election.



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# File 'lib/equalshares/election.rb', line 12

def initialize(instance, params = Params.new)
  @instance = instance
  @params = params
  @exact = params.accuracy == "fractions"
  @costs = instance.project_ids.to_h { |c| [c, numeric(instance.projects[c]["cost"])] }
  @float_costs = instance.project_ids.to_h { |c| [c, Float(instance.projects[c]["cost"])] }
end

Instance Attribute Details

#costs ⇒ Object (readonly)

Per-project cost in the accuracy's numeric type, as a Hash=> Numeric.



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# File 'lib/equalshares/election.rb', line 41

def costs
  @costs
end

#float_costs ⇒ Object (readonly)

Per-project cost as floats, as a Hash=> Float (for statistics and the cost/comparison bookkeeping that the equalshares.net tool always does in floats).



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# File 'lib/equalshares/election.rb', line 45

def float_costs
  @float_costs
end

#instance ⇒ Object (readonly)

Returns the value of attribute instance.



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# File 'lib/equalshares/election.rb', line 10

def instance
  @instance
end

#params ⇒ Object (readonly)

Returns the value of attribute params.



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# File 'lib/equalshares/election.rb', line 10

def params
  @params
end

Class Method Details

.rational_of(value) ⇒ Object

Exact rational from a cost/budget string, matching fraction.js's decimal handling ("5000" -> 5000, "5000.5" -> 10001/2).



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# File 'lib/equalshares/election.rb', line 71

def self.rational_of(value)
  Rational(value.to_s)
rescue ArgumentError
  Float(value).to_r
end

Instance Method Details

#approvers ⇒ Object 



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# File 'lib/equalshares/election.rb', line 28

def approvers
  instance.approvers
end

#budget ⇒ Object 



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# File 'lib/equalshares/election.rb', line 47

def budget
  @budget ||= numeric(instance.budget)
end

#exact? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/equalshares/election.rb', line 36

def exact?
  @exact
end

#float_budget ⇒ Object 



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# File 'lib/equalshares/election.rb', line 51

def float_budget
  @float_budget ||= Float(instance.budget)
end

#numeric(value) ⇒ Object

Convert a cost/budget/score string to the accuracy's numeric type.



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# File 'lib/equalshares/election.rb', line 65

def numeric(value)
  @exact ? self.class.rational_of(value) : Float(value)
end

#project_ids ⇒ Object 



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# File 'lib/equalshares/election.rb', line 24

def project_ids
  instance.project_ids
end

#statistics(winners) ⇒ Object 



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# File 'lib/equalshares/election.rb', line 60

def statistics(winners)
  Statistics.gather(voter_ids, @float_costs, instance.approvers, winners)
end

#supporters(project_id) ⇒ Object 



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# File 'lib/equalshares/election.rb', line 32

def supporters(project_id)
  instance.approvers[project_id]
end

#utilities(project_id) ⇒ Object

Per-project voter utilities for cardinal/ordinal ballots: { voter_id => Numeric }.



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# File 'lib/equalshares/election.rb', line 56

def utilities(project_id)
  (instance.scores[project_id] || {}).transform_values { |score| numeric(score) }
end

#voter_ids ⇒ Object 



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# File 'lib/equalshares/election.rb', line 20

def voter_ids
  instance.voter_ids
end