/*****
* callable.h
* Tom Prince 2005/06/19
*
* Runtime representation of functions.
*****/

#ifndef CALLABLE_H
#define CALLABLE_H

#include "common.h"
#include "item.h"
#include "inst.h"

namespace vm {

class stack;
typedef void (*bltin)(stack *s);

struct callable : public gc
{
 virtual void call(stack *) = 0;
 virtual ~callable();
 virtual bool compare(callable*) { return false; }

 // For debugging:
 virtual void print(ostream& out) = 0;
};

class nullfunc : public callable
{
private:
 nullfunc() {}
 static nullfunc func;
public:
 virtual void call (stack*);
 virtual bool compare(callable*);
 static callable* instance() { return &func; }

 void print(ostream& out);
};

// How a function reference to a non-builtin function is stored.
struct func : public callable {
 lambda *body;
 vmFrame *closure;
 func () : body(), closure() {}
 virtual void call (stack*);
 virtual bool compare(callable*);

 void print(ostream& out);
};

class bfunc : public callable
{
public:
 bfunc(bltin b) : func(b) {}
 virtual void call (stack *s) { func(s); }
 virtual bool compare(callable*);

 void print(ostream& out);
private:
 bltin func;
};

class thunk : public callable
{
public:
 thunk(callable *f, item i) : func(f), arg(i) {}
 virtual void call (stack*);

 void print(ostream& out);
private:
 callable *func;
 item arg;
};

inline ostream& operator<< (ostream& out, callable &c) {
 c.print(out);
 return out;
}

} // namespace vm

GC_DECLARE_PTRFREE(vm::nullfunc);

// I believe this is safe, as pointers to C++ functions do not point to
// the heap.
GC_DECLARE_PTRFREE(vm::bfunc);

#endif // CALLABLE_H