> Common Lisp is a programming language like any other: people who write good code in other languages can write good code in Common Lisp, and people who write bad code can make everyone's life just as miserable.
We're not talking about the extremes, here, though; we're talking about completely average code, written by completely average programmers, and the comparative number of extra milliseconds it takes these programmers to comprehend, or recall, the correct syntax in one language vs. another.
Milliseconds matter; when Google shaves milliseconds off their page load times, they earn millions of dollars. This isn't because every user is slightly better off, but because some discrete number of users switched from "eh, this is taking too long, I'm outta here" to "alright, I'll put up with that." People get fed up with programming languages all the time, but no one bothers to find a formal reason for it. Has anyone ever done an eye-tracking study on people programming?
> I am of the opinion that anyone who calls Common Lisp a "theoretically-pure" language
No one's doing that. "Lisp" as a general term does not mean "Common Lisp"; it refers to the feature intersection of all popularly-implemented Lisps—the "Lisp" that Greenspun's rule refers to getting implemented everywhere. That "Lisp" is very pure.
Greenspun's rule refers specifically to Common Lisp ("... of half of Common Lisp.") and there's no way that "half of Common Lisp", even with a healthy dose of hyperbole, can refer to the feature-intersection of all popularly-implemented Lisps, nor to anything "very pure".
We're not talking about the extremes, here, though; we're talking about completely average code, written by completely average programmers, and the comparative number of extra milliseconds it takes these programmers to comprehend, or recall, the correct syntax in one language vs. another.
Milliseconds matter; when Google shaves milliseconds off their page load times, they earn millions of dollars. This isn't because every user is slightly better off, but because some discrete number of users switched from "eh, this is taking too long, I'm outta here" to "alright, I'll put up with that." People get fed up with programming languages all the time, but no one bothers to find a formal reason for it. Has anyone ever done an eye-tracking study on people programming?
> I am of the opinion that anyone who calls Common Lisp a "theoretically-pure" language
No one's doing that. "Lisp" as a general term does not mean "Common Lisp"; it refers to the feature intersection of all popularly-implemented Lisps—the "Lisp" that Greenspun's rule refers to getting implemented everywhere. That "Lisp" is very pure.