Efficiency Concerns Top Old CL Compatibility
Following is a list of all known incompatibilities between this package and Common Lisp as documented in Steele (2nd edition).
Certain function names, such as
floor, were already taken by (incompatible) Emacs Lisp
functions; this package appends `
*' to the names of its
Common Lisp versions of these functions.
defun* is required instead of
defun in order
to use extended Common Lisp argument lists in a function. Likewise,
function* are versions of those forms
which understand full-featured argument lists. The
keyword does not work in
defmacro argument lists (except
inside recursive argument lists).
In order to allow an efficient implementation, keyword arguments use
a slightly cheesy parser which may be confused if a keyword symbol
is passed as the value of another keyword argument.
(memq :keyword rest-of-arguments)
is used to scan for
:keyword among the supplied
equal predicates do not distinguish
between IEEE floating-point plus and minus zero. The
predicate has several differences with Common Lisp; see Predicates.
setf mechanism is entirely compatible, except that
setf-methods return a list of five values rather than five
values directly. Also, the new ``
setf function'' concept
(defun (setf foo) ...)) is not implemented.
do-all-symbols form is the same as
with no obarray argument. In Common Lisp, this form would
iterate over all symbols in all packages. Since Emacs obarrays
are not a first-class package mechanism, there is no way for
do-all-symbols to locate any but the default obarray.
loop macro is complete except that
and type specifiers are unimplemented.
The multiple-value return facility treats lists as multiple
values, since Emacs Lisp cannot support multiple return values
directly. The macros will be compatible with Common Lisp if
values-list is always used to return to
multiple-value-bind or other multiple-value receiver;
values is used without
or vice-versa the effect will be different from Common Lisp.
Many Common Lisp declarations are ignored, and others match
the Common Lisp standard in concept but not in detail. For
special declarations, which are purely
advisory in Emacs Lisp, do not rigorously obey the scoping rules
set down in Steele's book.
*gensym-counter* starts out with a pseudo-random
value rather than with zero. This is to cope with the fact that
generated symbols become interned when they are written to and
loaded back from a file.
defstruct facility is compatible, except that structures
are of type
:type vector :named by default rather than some
special, distinct type. Also, the
:type slot option is ignored.
The second argument of
check-type is treated differently.