mathexpr.hh

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 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
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 * terms below provided that you ensure that this notice is replicated
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 * modified or unmodified, in source code or in binary form.
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 * met: redistributions of source code must retain the above copyright
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#ifndef __SIM_MATHEXPR_HH__
#define __SIM_MATHEXPR_HH__
 
#include <algorithm>
#include <array>
#include <functional>
#include <string>
#include <vector>
 
class MathExpr {
  public:
 
    MathExpr(std::string expr);
 
    typedef std::function<double(std::string)> EvalCallback;
 
    std::string toStr() const { return toStr(root, ""); }
 
    double eval(EvalCallback fn) const { return eval(root, fn); }
 
    std::vector<std::string> getVariables() const
    {
        std::vector<std::string> vars;
        getVariables(root, vars);
        return vars;
    }
 
  private:
    enum Operator {
        bAdd, bSub, bMul, bDiv, bPow, uNeg, sValue, sVariable, nInvalid
    };
 
    // Match operators
    const int MAX_PRIO = 4;
    typedef double (*binOp)(double, double);
    struct OpSearch {
        bool binary;
        Operator op;
        int priority;
        char c;
        binOp fn;
    };
 
    std::array<OpSearch, uNeg + 1> ops;
 
    class Node {
      public:
        Node() : op(nInvalid), l(0), r(0), value(0) {}
        std::string toStr() const {
            const char opStr[] = {'+', '-', '*', '/', '^', '-'};
            switch (op) {
              case nInvalid:
                return "INVALID";
              case sVariable:
                return variable;
              case sValue:
                return std::to_string(value);
              default:
                return std::string(1, opStr[op]);
            };
        }
 
        Operator op;
        Node *l, *r;
        double value;
        std::string variable;
    };
 
    Node * root;
 
    Node *parse(std::string expr);
 
    std::string toStr(Node *n, std::string prefix) const;
 
    double eval(const Node *n, EvalCallback fn) const;
 
    void getVariables(const Node *n, std::vector<std::string> &vars) const;
};
 
#endif