SCM_CLASS_SYS_GROUP 2698 src/gauche.h   #define SCM_SYS_GROUP_P(obj)   (SCM_XTYPEP(obj, SCM_CLASS_SYS_GROUP))
SCM_CLASS_SYS_GROUP  993 src/system.c       SCM_SET_CLASS(sg, SCM_CLASS_SYS_GROUP);