/* puz.gr -- elkhound grammar for puz.
   Copyright (C) 2007 Casey Marshall <csm@soe.ucsc.edu> */

verbatim {
  #include "TokenCode.h"
}

context_class PuzContext : public UserActions {
 public:

  virtual ~PuzContext() { }

  class expression
  {
  protected:
    expression *r, *l;
    expression() { }
  public:
    expression(expression *l, expression *r) : r(r), l(l) { }
    virtual double eval() { return 0.0; }
  };

  class add_expr : public expression
  {
  public:
    add_expr(expression *l, expression *r) : expression(l, r) { }
    virtual double eval() { return l->eval() + r->eval(); }
  };

  class sub_expr : public expression
  {
  public:
    sub_expr(expression *l, expression *r) : expression(l, r) { }
    virtual double eval() { return l->eval() - r->eval(); }
  };

  class times_expr : public expression
  {
  public:
    times_expr(expression *l, expression *r) : expression(l, r) { }
    virtual double eval() { return l->eval() * r->eval(); }
  };

  class div_expr : public expression
  {
  public:
    div_expr(expression *l, expression *r) : expression(l, r) { }
    virtual double eval() { return l->eval() / r->eval(); }
  };

  class literal : public expression
  {
  private:
    double value;

  public:
    literal(double value) : value(value) { }
    virtual double eval() { return value; }
  };

  class distance : public expression
  {
  private:
    TokenCode kind;
  public:
    distance(TokenCode kind) : kind(kind) { }
    virtual double eval()
    {
      extern double edgeDistance;
      extern double manhattanDistance;
      extern double manhattanDistanceNoBlank;
      extern double neighborDistance;
      extern double neighborDistanceNoBlank;

      switch (kind)
        {
        case TOK_EDGE: return edgeDistance;
        case TOK_MANHATTAN: return manhattanDistance;
        case TOK_MANHATTAN2: return manhattanDistanceNoBlank;
        case TOK_NEIGHBOR: return neighborDistance;
        case TOK_NEIGHBOR2: return neighborDistanceNoBlank;
        default:
          return 0.0;
        }
    }
  };
};

terminals {
  include("tokens.tok")

  token(double *) TOK_LITERAL;

  precedence {
    left 20 TOK_DIVIDE TOK_TIMES;
    left 10 TOK_PLUS TOK_MINUS;
  }
}

nonterm(PuzContext::expression*) Expr {
  -> n:TOK_LITERAL  { double v = *n; delete n; return new PuzContext::literal(v); }
  -> TOK_EDGE       { return new PuzContext::distance(TOK_EDGE); }
  -> TOK_MANHATTAN  { return new PuzContext::distance(TOK_MANHATTAN); }
  -> TOK_MANHATTAN2 { return new PuzContext::distance(TOK_MANHATTAN2); }
  -> TOK_NEIGHBOR   { return new PuzContext::distance(TOK_NEIGHBOR); }
  -> TOK_NEIGHBOR2  { return new PuzContext::distance(TOK_NEIGHBOR2); }
  -> e1:Expr TOK_PLUS e2:Expr   { return new PuzContext::add_expr(e1, e2); }
  -> e1:Expr TOK_MINUS e2:Expr  { return new PuzContext::sub_expr(e1, e2); }   
  -> e1:Expr TOK_TIMES e2:Expr  { return new PuzContext::times_expr(e1, e2); }
  -> e1:Expr TOK_DIVIDE e2:Expr { return new PuzContext::div_expr(e1, e2); }
  -> TOK_LPAREN e:Expr TOK_RPAREN { return e; }
}