Class: MIPPeR::LinExpr

Inherits:
Object
  • Object
show all
Defined in:
lib/mipper/expression.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(terms = {}) ⇒ LinExpr

Returns a new instance of LinExpr.



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# File 'lib/mipper/expression.rb', line 5

def initialize(terms = {})
  @terms = terms
end

Instance Attribute Details

#terms ⇒ Object (readonly)

Returns the value of attribute terms.



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# File 'lib/mipper/expression.rb', line 3

def terms
  @terms
end

Instance Method Details

#+(other) ⇒ Object

Add two MIPPeR::LinExprs



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# File 'lib/mipper/expression.rb', line 10

def +(other)
  case other
  when LinExpr
    # Add the terms of two expressions
    # For now, this assumes variables are not duplicated
    LinExpr.new(@terms.merge(other.terms) { |_, c1, c2| c1 + c2 })
  when Variable
    # Add the variable to the expression
    self + other * 1.0
  else
    fail TypeError
  end
end

#add(other) ⇒ Object

Add terms from the other expression to this one



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# File 'lib/mipper/expression.rb', line 25

def add(other)
  case other
  when LinExpr
    @terms.merge!(other.terms) { |_, c1, c2| c1 + c2 }
  when Variable
    if @terms.key? other
      @terms[other] += 1.0
    else
      @terms[other] = 1.0
    end
  else
    fail TypeError
  end

  self
end

#inspect ⇒ Object

Produce a string representing the expression



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# File 'lib/mipper/expression.rb', line 43

def inspect
  @terms.map do |var, coeff|
    # Skip if the coefficient is zero or the value is zero
    value = var.value
    next if coeff == 0 || value == 0 || value == false

    coeff == 1 ? var.name : "#{var.name} * #{coeff}"
  end.compact.join(' + ')
end