rule              489 src/macro.c            ScmObj rule = SCM_CAR(rp);
rule              490 src/macro.c            if (Scm_Length(rule) != 2) goto badform;
rule              499 src/macro.c            ctx.form = SCM_CAR(rule);
rule              503 src/macro.c            ctx.form = SCM_CADR(rule);