Well, except that C isn't a family of languages. (EDIT: or rather there is a specific language with the proper name "The C Programming Language," whereas there is no specific programming language called "lisp." EDIT: except McCarthy's?) I guess if we were to follow this line of reasoning, all the languages you mention are in a family of ALGOL-like language.
Emacs Lisp is also pretty darned incompatible with Common Lisp. Is Emacs Lisp not a lisp? How about Scheme? Is Scheme not a lisp?
The way you refer to Lisp, capitalized and as a proper noun, suggests to me that you are simply using "Lisp" as an abbreviated form of "ANSI Common Lisp."
If one chooses a definition of lisp that only includes Common Lisp, then no other lisp can be a lisp unless it implements the ANSI Common Lisp spec (is SBCL a lisp? I hear they added TCO, which isn't in the spec). But most people consider Emacs Lisp, Scheme, and indeed Clojure a lisp.
I've seen the lisp means Common Lisp argument elsewhere before, but at this point it just sounds like sour grapes coupled with an odd minority viewpoint around semantics.
> Emacs Lisp is also pretty darned incompatible with Common Lisp
Not true, both have the core of McCarthy's Lisp and are in the Maclisp line...
> If one chooses a definition of lisp that only includes Common Lisp
Nobody does that.
> , then no other lisp can be a lisp unless it implements the ANSI Common Lisp spec (is SBCL a lisp? I hear they added TCO, which isn't in the spec).
How is that relevant? Garbage Collection is also not in the spec. Lot's of random stuff is not in the spec.
> But most people consider Emacs Lisp, Scheme, and indeed Clojure a lisp.
Since "most people" don't even know what Lisp is, nothing follows from this.
> I've seen the lisp means Common Lisp argument elsewhere
Defintely elsewhere. It hasn't been made here.
First rule: if the thing has not Lisp in its name, it probably is not a Lisp.
Second rule: if it is not somewhat compatible with Lisp 1, then it is not a Lisp.
From that you can infer that languages like Lisp 1, Lisp 1.5, Lisp 2, Maclisp, BBN Lisp, UCI Lisp, VAX Lisp, Spice Lisp, New Implementation Lisp, Zetalisp, Franz Lisp, Standard Lisp, Interlisp, Eulisp, LeLisp, Mulisp, Emacs Lisp, Xlisp, Common Lisp, various Common Lisp derived languages, ISLisp, are all direct Lisp dialects.
C is certainly a family of languages: K&R "Classic" C, GNU C, ISO {C90, C99, C11}, MS Visual C, Borland Turbo C, ... interpreters like EiC. There are many C toolchains from all sorts of embedded vendors: like for Microchip's PIC, Atmel AVR.
C++ is in the C family; many C programs run as C++ with only small modifications and some cases no modifications at all.
Objective C is another C family member.
I maintain a fairly large FOSS project in such a way that although it is written in C, you can configure to use a C++ compiler; effectively, C++ is a target platform to which the code is portable. It's just another C dialect.
Fair enough: C# is a Java, which, in turn, is a C dialect. Wee!
I just cribbed the following from a page about Javascript:
it would be trivial to make it work in C++ code and carry out the same intent.Thus Javascript is just a C++, unless you're petty.
Clojure is less compatible with Lisp than this Javascript-C++ relationship, though; yet, why split hairs.