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Expression

  • java.lang.Object
    • com.dashoptimization.objects.Expression
  • Direct Known Subclasses:
    AbstractExpression, Variable 
    public abstract class Expression
extends java.lang.Object
    Base class for all expressions. Expressions are the building blocks for all constraints represented by Inequality and also for indicator constraints. Expressions are created by combining variables and constant using operators and functions. The operators available for combining constants, variables and expressions are plus, minus, mul (multiply) and div (divide) and are defined as member functions of the Expression class (or its subclasses). To add two variables x and y one would do ce. x.plus(y). To create the expression 2x + 3y one could write x.mul(2).plus(y.mul(3)). The functions that can be used to combine expressions can be found in the Utils class. Examples are sum, sin, etc. Expressions are unmodifiable and are represented as expression trees. This means that all operators are implemented to take only constant time to produce the result. An exception to the above are linear and quadratic expressions (class LinExpression and QuadExpression). Linear and quadratic expressions are very common to math programming and thus they can be built in even more efficient ways: The LinExpression and QuadExpression are the only mutable expressions. They can be modified using the addTerm() family of functions. When creating a linear expression like 2x+3y+4z then it is more efficient to do this as LinExpression.create().addTerm(x,2).addTerm(y,3).addTerm(z,4) than to create the expression using operators plus and mul. For short expressions the performance difference will not be measurable but for longer expressions it will start to matter. Since operators copy their argument expressions by reference, care must be taken when applying operators to LinExpression or QuadExpression: when changing an instance of LinExpression or QuadExpression, this will implicitly change any other expression that references this expression through operators or functions.
    Since:
    43.00

    • Constructor Summary

      Constructor Description
      Expression()  

    • Method Summary

      Modifier and Type Method Description
      Expression div​(double arg)
      Create a new expression that represents the quotient of this and arg.
      Expression div​(Expression arg)
      Create a new expression that represents the quotient of this and arg.
      abstract Inequality.Definition eq​(double rhs)
      Create an "equals" constraint with this expression as left-hand side.
      abstract Inequality.Definition eq​(Expression rhs)
      Create an "equals" constraint with this expression as left-hand side.
      abstract double evaluate​(double[] solution)
      Compute the value of this expression with respect to the given solution vector (which is not required to be feasible).
      abstract Inequality.Definition geq​(double rhs)
      Create a "greater than or equal" constraint with this expression as left-hand side.
      abstract Inequality.Definition geq​(Expression rhs)
      Create a "greater than or equal" constraint with this expression as left-hand side.
      abstract double getConstantView()
      Get the constant value to which this expression evaluates.
      abstract LinearView getLinearView()
      Get a linear read-only view on this expression.
      abstract int getMaxDegree()
      Get the maximum degree of any of the terms/monomials that appear in the symbolic representation of all parenthesized sub-expressions are fully expanded.
      abstract QuadView getQuadView()
      Get a quadratic read-only view on this expression.
      abstract Inequality.Definition in​(double lb, double ub)
      Create a range constraint that bounds this expression from below and above.
      abstract Inequality.Definition leq​(double rhs)
      Create a "less than or equal" constraint with this expression as left-hand side.
      abstract Inequality.Definition leq​(Expression rhs)
      Create a "less than or equal" constraint with this expression as left-hand side.
      Expression minus​(double arg)
      Create a new expression that represents the difference of this and arg.
      Expression minus​(Expression arg)
      Create a new expression that represents the difference of this and arg.
      Expression mul​(double arg)
      Create a new expression that represents the product of this and arg.
      Expression mul​(Expression arg)
      Create a new expression that represents the product of this and arg.
      Expression plus​(double arg)
      Create a new expression that represents the sum of this and arg.
      Expression plus​(Expression arg)
      Create a new expression that represents the sum of this and arg.
      Expression uminus()
      Create a new expression that represents the unary minus of this one.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Parent Topic Class Summary

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