subtypep: structs with car or length method are sequences.

* lib.c (subtypep): For the sequence supertype, check
whether the subtype is a structure that has a length or
car method, returning t if so.

* struct.c (get_special_slot_by_type): New function.

* struct.h (get_special_slot_by_type): Declared.

* txr.1: Add <structures with cars or length methods> to the
type hierarchy diagram.

1 files changed, 1 insertions, 0 deletions

diff --git a/struct.h b/struct.h
index 385d8dd4..1850814e 100644
--- a/struct.h
+++ b/struct.h
@@ -87,5 +87,6 @@ val static_slot_types(val slot);
 val slot_type_reg(val slot, val strct);
 val static_slot_type_reg(val slot, val strct);
 val get_special_slot(val obj, enum special_slot spidx);
+val get_special_slot_by_type(val stype, enum special_slot spidx);
 INLINE int obj_struct_p(val obj) { return obj->co.ops == &struct_inst_ops; }
 void struct_init(void);