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#ifndef LINPROG_MODEL_H
#define LINPROG_MODEL_H
#include <vector>
#include <utility>
#include "stl-helper.h"
typedef std::pair<double, unsigned int> Term;
typedef std::vector<Term> Terms;
class LinearExpression
{
private:
Terms terms;
public:
void add_term(double coefficient, unsigned int variable_index)
{
terms.push_back(Term(coefficient, variable_index));
}
// by default, assumes coefficient == 1
void add_var(unsigned int variable_index)
{
add_term(1.0, variable_index);
}
const Terms& get_terms(void) const
{
return terms;
}
bool has_terms(void) const
{
return !terms.empty();
}
};
typedef std::pair<LinearExpression *, double> Constraint;
typedef std::vector<Constraint> Constraints;
// builds a maximization problem piece-wise
class LinearProgram
{
// the function to be maximized
LinearExpression *objective;
// linear expressions constrained to an exact value
Constraints equalities;
// linear expressions constrained by an upper bound (exp <= bound)
Constraints inequalities;
public:
LinearProgram() : objective(new LinearExpression()) {};
~LinearProgram()
{
delete objective;
foreach(equalities, eq)
delete eq->first;
foreach(inequalities, ineq)
delete ineq->first;
}
void set_objective(LinearExpression *exp)
{
delete objective;
objective = exp;
}
void add_inequality(LinearExpression *exp, double upper_bound)
{
if (exp->has_terms())
inequalities.push_back(Constraint(exp, upper_bound));
else
delete exp;
}
void add_equality(LinearExpression *exp, double equal_to)
{
if (exp->has_terms())
inequalities.push_back(Constraint(exp, equal_to));
else
delete exp;
}
const LinearExpression *get_objective() const
{
return objective;
}
LinearExpression *get_objective()
{
return objective;
}
const Constraints& get_equalities() const
{
return equalities;
}
const Constraints& get_inequalities() const
{
return inequalities;
}
};
#endif
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