prop-src/patenv.h

   1 #ifndef interface_to_the_scanner_h
   2 #define interface_to_the_scanner_h
   3
   4 #include <AD/generic/generic.h>
   5 #include "ir.h"
   6 #include "ast.h"
   7
   8 /////////////////////////////////////////////////////////////////////////////
   9 // An environment of pattern variables is implemented as a pair of
  10 // stacks, one caching the current set of bindings and one registering
  11 // the lexical scope boundaries.
  12 /////////////////////////////////////////////////////////////////////////////
  13 class PatternVarEnv {
  14
  15    PatternVarEnv(const PatternVarEnv&);     // no copy constructor
  16    void operator = (const PatternVarEnv&);  // no assignment
  17
  18 protected:
  19
  20    //////////////////////////////////////////////////////////////////////////
  21    // The environment is implemented as two stacks, one storing
  22    // the bindings and the other storing the highwater mark of each scope.
  23    //////////////////////////////////////////////////////////////////////////
  24
  25    class PatternVarEnv_Impl * impl;
  26
  27 public:
  28
  29    //////////////////////////////////////////////////////////////////////////
  30    // Constructor and destructor
  31    //////////////////////////////////////////////////////////////////////////
  32    PatternVarEnv (int max_size = 256, int max_levels = 256);
  33   ~PatternVarEnv ();
  34
  35    //////////////////////////////////////////////////////////////////////////
  36    // Add binding and lookup binding
  37    //////////////////////////////////////////////////////////////////////////
  38    Exp  add( Id,                    // name of pattern variable
  39              Exp,                   // binding expression
  40              Ty,                    // type of pattern variable
  41              Polarity = ISpositive  // polarity of the pattern
  42            );
  43    Exp  lookup(Id, Bool * = 0);  // lookup old binding, returns NIL if not found.
  44                                  // returns true as second argument iff the
  45                                  // binding is from the current scope.
  46    Exp  guard ();                // current guard expression
  47    Exp  guard (Exp);             // current guard expression
  48    void add_guard (Exp);
  49    Bool separate_guard ();
  50    Bool tree_grammar   ();
  51    //////////////////////////////////////////////////////////////////////////
  52    // Enter and leave scope.
  53    // As a default, we allow only linear patterns.
  54    //////////////////////////////////////////////////////////////////////////
  55    void new_scope( Bool linear_patterns = true,    // enters new scope
  56                    Bool separate_guard  = false,   // separate the guard
  57                    Bool treegrammar     = false ); // tree grammar mode
  58    void old_scope();                               // returns to old scope
  59 };
  60
  61 extern PatternVarEnv pv_env;
  62
  63 #endif