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/*****
* inst.h
* Tom Prince and John Bowman 2005/04/12
*
* Descibes the items that are used by the virtual machine.
*****/
#ifndef ITEM_H
#define ITEM_H
#include "common.h"
#include <cfloat>
#include <cmath>
#include <typeinfo>
#include <cassert>
namespace vm {
class item;
class bad_item_value {};
template<typename T>
T get(const item&);
#if COMPACT
// Identify a default argument.
extern const Int DefaultValue;
// Identify an undefined item.
extern const Int Undefined;
#endif
extern const item Default;
class item : public gc {
private:
#if !COMPACT
const std::type_info *kind;
#endif
union {
Int i;
double x;
bool b;
void *p;
};
public:
#if COMPACT
bool empty() const
{return i >= Undefined;}
item() : i(Undefined) {}
item(Int i)
: i(i) {}
item(int i)
: i(i) {}
item(double x)
: x(x) {}
item(bool b)
: b(b) {}
item& operator= (int a)
{ i=a; return *this; }
item& operator= (Int a)
{ i=a; return *this; }
item& operator= (double a)
{ x=a; return *this; }
item& operator= (bool a)
{ b=a; return *this; }
template<class T>
item(T *p)
: p((void *) p) {
assert(p < (void *) Undefined);
}
template<class T>
item(const T &P)
: p(new(UseGC) T(P)) {
assert(p < (void *) Undefined);
}
template<class T>
item& operator= (T *a)
{ p=(void *) a; return *this; }
template<class T>
item& operator= (const T &it)
{ p=new(UseGC) T(it); return *this; }
#else
bool empty() const
{return *kind == typeid(void);}
item()
: kind(&typeid(void)) {}
item(Int i)
: kind(&typeid(Int)), i(i) {}
item(int i)
: kind(&typeid(Int)), i(i) {}
item(double x)
: kind(&typeid(double)), x(x) {}
item(bool b)
: kind(&typeid(bool)), b(b) {}
item& operator= (int a)
{ kind=&typeid(Int); i=a; return *this; }
item& operator= (Int a)
{ kind=&typeid(Int); i=a; return *this; }
item& operator= (double a)
{ kind=&typeid(double); x=a; return *this; }
item& operator= (bool a)
{ kind=&typeid(bool); b=a; return *this; }
template<class T>
item(T *p)
: kind(&typeid(T)), p((void *) p) {}
template<class T>
item(const T &p)
: kind(&typeid(T)), p(new(UseGC) T(p)) {}
template<class T>
item& operator= (T *a)
{ kind=&typeid(T); p=(void *) a; return *this; }
template<class T>
item& operator= (const T &it)
{ kind=&typeid(T); p=new(UseGC) T(it); return *this; }
const std::type_info &type() const
{ return *kind; }
#endif
template<typename T>
friend inline T get(const item&);
friend inline bool isdefault(const item&);
friend ostream& operator<< (ostream& out, const item& i);
private:
template <typename T>
struct help;
template <typename T>
struct help<T*> {
static T* unwrap(const item& it)
{
#if COMPACT
if(!it.empty())
return (T*) it.p;
#else
if(*it.kind == typeid(T))
return (T*) it.p;
#endif
throw vm::bad_item_value();
}
};
template <typename T>
struct help {
static T& unwrap(const item& it)
{
#if COMPACT
if(!it.empty())
return *(T*) it.p;
#else
if(*it.kind == typeid(T))
return *(T*) it.p;
#endif
throw vm::bad_item_value();
}
};
};
class frame : public gc {
#ifdef DEBUG_FRAME
string name;
#endif
typedef mem::vector<item> vars_t;
vars_t vars;
public:
#ifdef DEBUG_FRAME
frame(string name, size_t size)
: name(name), vars(size)
{}
string getName() { return name; }
#else
frame(size_t size)
: vars(size)
{}
#endif
item& operator[] (size_t n)
{ return vars[n]; }
item operator[] (size_t n) const
{ return vars[n]; }
size_t size()
{ return vars.size(); }
// Extends vars to ensure it has a place for any variable indexed up to n.
void extend(size_t n) {
if(vars.size() < n)
vars.resize(n);
}
};
template<typename T>
inline T get(const item& it)
{
return item::help<T>::unwrap(it);
}
template <>
inline int get<int>(const item&)
{
throw vm::bad_item_value();
}
template <>
inline Int get<Int>(const item& it)
{
#if COMPACT
if(!it.empty())
return it.i;
#else
if(*it.kind == typeid(Int))
return it.i;
#endif
throw vm::bad_item_value();
}
template <>
inline double get<double>(const item& it)
{
#if COMPACT
if(!it.empty())
return it.x;
#else
if(*it.kind == typeid(double))
return it.x;
#endif
throw vm::bad_item_value();
}
template <>
inline bool get<bool>(const item& it)
{
#if COMPACT
if(!it.empty())
return it.b;
#else
if(*it.kind == typeid(bool))
return it.b;
#endif
throw vm::bad_item_value();
}
#if !COMPACT
// This serves as the object for representing a default argument.
struct default_t : public gc {};
#endif
inline bool isdefault(const item& it)
{
#if COMPACT
return it.i == DefaultValue;
#else
return *it.kind == typeid(default_t);
#endif
}
ostream& operator<< (ostream& out, const item& i);
} // namespace vm
#endif // ITEM_H
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