+#define SCM_PROGRAM_FREE_VARIABLES(x) (SCM_CELL_OBJECT_LOC (x, 3))
+#define SCM_PROGRAM_FREE_VARIABLE_REF(x,i) (SCM_PROGRAM_FREE_VARIABLES (x)[i])
+#define SCM_PROGRAM_FREE_VARIABLE_SET(x,i,v) (SCM_PROGRAM_FREE_VARIABLES (x)[i]=(v))
+#define SCM_PROGRAM_NUM_FREE_VARIABLES(x) (SCM_CELL_WORD_0 (x) >> 16)