ffi: handle sub operation in carray.

Thus, [ca 3..5] syntax works for slice extraction.
However, this works referentially, not by making a copy.
The extracted subarray points to the original memory,
until carray-dup is invoked on it.

* ffi.c (carray_sub): New function.
(ffi_init): carray-sub intrinsic registered.

* ffi.h (carray_sub): Declared.

* lib.c (sub): Handle carray via carray_sub.

* txr.1: Documented changes in sub.

1 files changed, 1 insertions, 0 deletions

diff --git a/ffi.h b/ffi.h
index 2e88f167..4e45eaf2 100644
--- a/ffi.h
+++ b/ffi.h
@@ -104,6 +104,7 @@ val vec_carray(val carray, val null_term_p);
 val list_carray(val carray, val null_term_p);
 val carray_ref(val carray, val idx);
 val carray_refset(val carray, val idx, val newval);
+val carray_sub(val carray, val from, val to);
 val carray_get(val carray);
 val carray_getz(val carray);
 val carray_put(val array, val seq);