Port "Fcdr()" and "cdr()" to Rust

rust_src/src/cons.rs

@@ -113,12 +113,16 @@ unsafe fn XCAR(object: LispObject) -> LispObject {
     (*XCONS(object)).car
 }
 
-/// Take the car of a cons cell, or signal an error if it's a
+unsafe fn XCDR(object: LispObject) -> LispObject {
+    (*XCONS(object)).cdr
+}
+
+/// Take the car/cdr of a cons cell, or signal an error if it's a
 /// different type.
 ///
 /// # Porting Notes
 ///
-/// This is equivalent to `CAR` in C code.
+/// This is equivalent to `CAR`/`CDR` in C code.
 fn car(object: LispObject) -> LispObject {
     if CONSP(object) {
         unsafe {
@@ -132,6 +136,19 @@ fn car(object: LispObject) -> LispObject {
         }
     }
 }
+fn cdr(object: LispObject) -> LispObject {
+    if CONSP(object) {
+        unsafe {
+            XCDR(object)
+        }
+    } else if NILP(object) {
+        Qnil
+    } else {
+        unsafe {
+            wrong_type_argument(Qlistp, object)
+        }
+    }
+}
 
 #[no_mangle]
 pub extern "C" fn Fcar(list: LispObject) -> LispObject {
@@ -145,3 +162,16 @@ See Info node `(elisp)Cons Cells' for a discussion of related basic
 Lisp concepts such as car, cdr, cons cell and list.
 
 (fn LIST)");
+
+#[no_mangle]
+pub extern "C" fn Fcdr(list: LispObject) -> LispObject {
+    cdr(list)
+}
+
+defun!("cdr", Fcdr, Scdr, 1, 1, ptr::null(), " Return the cdr of LIST.  If arg is nil, return nil.
+Error if arg is not nil and not a cons cell.  See also `cdr-safe'.
+
+See Info node `(elisp)Cons Cells' for a discussion of related basic
+Lisp concepts such as cdr, car, cons cell and list.
+
+(fn LIST)");

rust_src/src/lib.rs

@@ -31,6 +31,7 @@ pub use math::Fquo;
 pub use cons::Fsetcar;
 pub use cons::Fsetcdr;
 pub use cons::Fcar;
+pub use cons::Fcdr;
 
 extern "C" {
     fn defsubr(sname: *const LispSubr);
@@ -55,6 +56,7 @@ pub extern "C" fn rust_init_syms() {
         defsubr(&*cons::Ssetcar);
         defsubr(&*cons::Ssetcdr);
         defsubr(&*cons::Scar);
+        defsubr(&*cons::Scdr);
         defsubr(&*strings::Sstringp);
         defsubr(&*strings::Seq);
         defsubr(&*strings::Snull);

src/data.c

@@ -479,17 +479,6 @@ DEFUN ("car-safe", Fcar_safe, Scar_safe, 1, 1, 0,
   return CAR_SAFE (object);
 }
 
-DEFUN ("cdr", Fcdr, Scdr, 1, 1, 0,
-       doc: /* Return the cdr of LIST.  If arg is nil, return nil.
-Error if arg is not nil and not a cons cell.  See also `cdr-safe'.
-
-See Info node `(elisp)Cons Cells' for a discussion of related basic
-Lisp concepts such as cdr, car, cons cell and list.  */)
-  (register Lisp_Object list)
-{
-  return CDR (list);
-}
-
 DEFUN ("cdr-safe", Fcdr_safe, Scdr_safe, 1, 1, 0,
        doc: /* Return the cdr of OBJECT if it is a cons cell, or else nil.  */)
   (Lisp_Object object)
@@ -3341,7 +3330,6 @@ syms_of_data (void)
   defsubr (&Ssubrp);
   defsubr (&Sbyte_code_function_p);
   defsubr (&Schar_or_string_p);
-  defsubr (&Scdr);
   defsubr (&Scar_safe);
   defsubr (&Scdr_safe);
   defsubr (&Ssymbol_function);

src/lisp.h

@@ -1276,6 +1276,7 @@ CDR_SAFE (Lisp_Object c)
 Lisp_Object Fsetcar(Lisp_Object, Lisp_Object);
 Lisp_Object Fsetcdr(Lisp_Object, Lisp_Object);
 Lisp_Object Fcar(Lisp_Object);
+Lisp_Object Fcdr(Lisp_Object);
 Lisp_Object Fatom(Lisp_Object);
 
 /* In a string or vector, the sign bit of the `size' is the gc mark bit.  */