[alpaca128]

Emacs Lisp doesn't have tail call optimization, just like the Lisp it was inspired by.

I'm definitely not an expert in that area, but this list seems kind of arbitrary to me. Especially with s-expressions being optional, which are probably the widest-known feature of the language. According to that definition, Haskell is a "true" Lisp but at least 2 Lisps are not. That makes no sense to me.

[webreac]

The last sentence was from me. The four items are from the SICP (not TAOCP, my mistake). They all are mandated by IEEE scheme standard.

I have encountered many functionnal languages when I was student (caml-light (the ancestor of ocaml), lelisp, gofer (a cousin of haskell), miranda, graal, FP systems, yafool).

The typing may be dynamic or static. The evaluation may be strict or lazy. They may have homoiconicity or a more suggared syntax. All theses choices are valid. These languages have in common the list of fundamental properties. IMHO, this list of 4 items encompass many aspects of SICP. When I evaluate a language, this list helps me understand the qualities and limitations of a language. For example, Perl5 does not have a true garbage collector. javascript does not have tail recursion. Knowing these limitations, I will not code the same way. In Perl5, I will take care of breaking unused circular data. In javascript, I will reorganise highly recursive algorithms.

[stewbrew]

Almost every language can do tail recursion (in most languages it will blow the stack though) but not every language does tail call optimization. This is a requirement for scheme but it is not for common lisp and many other lisps. So, I don't think this should be on the list.

[nicoburns]

JavaScript does have tail recursion in the spec, and JSC (Safari) implements it. Other runtimes have thus far refused to because it can impact on debugging I believe.