4 ms·

Lisp-1 vs Lisp-2 is about whether functions and other variables are in the same namespace or not. Packages are orthogonal to this. Also, generic functions in C

by jpr 16y ago

Lisp-1 vs Lisp-2 is about whether functions and other variables are in the same namespace or not. Packages are orthogonal to this. Also, generic functions in Common Lisp don't suffer from nearly the same amount of complexity as can be found in C++: there is always only one signature (lambda-list) for any function name, whether generic or not, there are no implicit conversions, no memory-allocation details, value/pointer/reference distinction, constness, virtualness, overloading of assignment operators etc.

Xurinos 16y ago
By your wording, aren't CL packages considered to be just an implementation of a namespace? Is there another way to declare symbol namespaces in CL (outside of rolling our own organisms)? I was under the impression that the function signature was not the issue raised... but the fact that the same function name could lead to completely different behaviors depending on a context. In the case of generic functions, the specific function implementation is usually (ignoring some of the other matching features) determined by the input types. The input types define the context. All that said, I realize now that this might be less of a problem in CL if you just group your defmethods in the same area. If the problem is grepping for the definition, it is easy enough to rearrange things so that the related functions are in a close-enough place. In C++, the classes try to own their methods -- with the exception of warily-regarded "friend" methods.
- jpr 16y ago
  Finding a method definition is quite easy in CL: just use the function 'find-method': http://www.cs.cmu.edu/Groups/AI/html/hyperspec/HyperSpec/Body/stagenfun_find-method.html http://www.cs.cmu.edu/Groups/AI/html/hyperspec/HyperSpec/Bod... Though grep would probably do just fine too, since method definitions are defined with 'defmethod' instead of 'defun', so you can see at a glance whether something is generic or not.
- jpr 16y ago
  About packages and namespaces: Package is essentially a collection that maps symbols to values. In CL packages have (at least) two namespaces: one for functions, other for any kind of variables. The reason for this is that when you write the form (fun #'a b) you and the compiler can be sure that 'fun' and 'a' are both meant to be functions. There are both advantages and disadvantages to this.

by jpr 16y ago

Xurinos 16y ago

By your wording, aren't CL packages considered to be just an implementation of a namespace? Is there another way to declare symbol namespaces in CL (outside of rolling our own organisms)? I was under the impression that the function signature was not the issue raised... but the fact that the same function name could lead to completely different behaviors depending on a context. In the case of generic functions, the specific function implementation is usually (ignoring some of the other matching features) determined by the input types. The input types define the context. All that said, I realize now that this might be less of a problem in CL if you just group your defmethods in the same area. If the problem is grepping for the definition, it is easy enough to rearrange things so that the related functions are in a close-enough place. In C++, the classes try to own their methods -- with the exception of warily-regarded "friend" methods.

jpr 16y ago
Finding a method definition is quite easy in CL: just use the function 'find-method': http://www.cs.cmu.edu/Groups/AI/html/hyperspec/HyperSpec/Body/stagenfun_find-method.html http://www.cs.cmu.edu/Groups/AI/html/hyperspec/HyperSpec/Bod... Though grep would probably do just fine too, since method definitions are defined with 'defmethod' instead of 'defun', so you can see at a glance whether something is generic or not.
jpr 16y ago
About packages and namespaces: Package is essentially a collection that maps symbols to values. In CL packages have (at least) two namespaces: one for functions, other for any kind of variables. The reason for this is that when you write the form (fun #'a b) you and the compiler can be sure that 'fun' and 'a' are both meant to be functions. There are both advantages and disadvantages to this.