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diff --git a/graphics/asymptote/program.h b/graphics/asymptote/program.h
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+/*****
+ * program.h
+ * Tom Prince
+ * 
+ * The list of instructions used by the virtual machine.
+ *****/
+
+#ifndef PROGRAM_H
+#define PROGRAM_H
+
+#include <cstddef> // for ptrdiff_t
+
+#include "common.h"
+#include "inst.h"
+
+using std::ptrdiff_t;
+
+namespace vm {
+struct inst;
+
+class program : public gc {
+public:
+  class label;
+  program();
+  void encode(inst i);
+  label begin();
+  label end();
+  inst &back();
+  void pop_back();
+private:
+  friend class label;
+  typedef mem::vector<inst> code_t;
+  code_t code;
+  inst& operator[](size_t);
+};
+
+class program::label
+{
+public: // interface
+  label() : where(0), code() {}
+public: //interface
+  label& operator++();
+  label& operator--();
+  bool defined() const;
+  bool operator==(const label& right) const;
+  bool operator!=(const label& right) const;
+  inst& operator*() const;
+  inst* operator->() const;
+  friend ptrdiff_t offset(const label& left,
+                          const label& right);
+private:
+  label (size_t where, program* code)
+    : where(where), code(code) {}
+  size_t where;
+  program* code;
+  friend class program;
+};
+
+// Prints one instruction (including arguments).
+void printInst(std::ostream& out, const program::label& code,
+               const program::label& base);
+
+// Prints code until a ret opcode is printed.
+void print(std::ostream& out, program *base);
+
+// Inline forwarding functions for vm::program
+inline program::program()
+  : code() {}
+inline program::label program::end()
+{ return label(code.size(), this); }
+inline program::label program::begin()
+{ return label(0, this); }
+inline inst& program::back()
+{ return code.back(); }
+inline void program::pop_back()
+{ return code.pop_back(); }
+inline void program::encode(inst i)
+{ code.push_back(i); }
+inline inst& program::operator[](size_t n)
+{ return code[n]; }
+inline program::label& program::label::operator++()
+{ ++where; return *this; }
+inline program::label& program::label::operator--()
+{ --where; return *this; }
+inline bool program::label::defined() const
+{ return (code != 0); }
+inline bool program::label::operator==(const label& right) const
+{ return (code == right.code) && (where == right.where); }
+inline bool program::label::operator!=(const label& right) const
+{ return !(*this == right); }
+inline inst& program::label::operator*() const
+{ return (*code)[where]; }
+inline inst* program::label::operator->() const
+{ return &**this; }
+inline ptrdiff_t offset(const program::label& left,
+                        const program::label& right)
+{ return right.where - left.where; }
+
+} // namespace vm
+
+#endif // PROGRAM_H