prod.hh

/// @file
/// @brief Base class for grammar productions

#include <string>
#include <iostream>

#ifndef PROD_HH
#define PROD_HH

/// Base class for walking the AST
struct prod_visitor {
  virtual void visit(struct prod *p) = 0;
  virtual ~prod_visitor() { }
};

/// Base class for AST nodes
struct prod {
  /// Parent production that instanciated this one.  May be NULL for
  /// top-level productions.
  struct prod *pprod;
  /// Scope object to model column/table reference visibility.
  struct scope *scope;
  /// Level of this production in the AST.  0 for root node.
  int level;
  /// Number of retries in this production.  Child productions are
  /// generated speculatively and may fail.
  long retries = 0;
  /// Maximum number of retries allowed before reporting a failure to
  /// the Parent prod.
  long retry_limit = 200;
  prod(prod *parent);
  /// Newline and indent according to tree level.
  virtual void indent(std::ostream &out);
  /// Emit SQL for this production.
  virtual void out(std::ostream &out) = 0;
  /// Check with the impedance matching code whether this production
  /// has been blacklisted and throw an exception.
  virtual void match();
  /// Visitor pattern for walking the AST.  Make sure you visit all
  /// child production when deriving classes.
  virtual void accept(prod_visitor *v) { v->visit(this); }
  /// Report a "failed to generate" error.
  virtual void fail(const char *reason);
  /// Increase the retry count and throw an exception when retry_limit
  /// is exceeded.
  void retry();
};

inline std::ostream& operator<<(std::ostream& s, prod& p)
{
  p.out(s); return s;
}

#endif