[TUHS] Happy birthday, Niklaus Wirth!
crossd at gmail.com
Fri Feb 16 12:51:20 AEST 2018
On Thu, Feb 15, 2018 at 9:41 PM, Larry McVoy <lm at mcvoy.com> wrote:
> On Thu, Feb 15, 2018 at 09:38:02PM -0500, Dan Cross wrote:
> > On Thu, Feb 15, 2018 at 8:56 PM, Lawrence Stewart <stewart at serissa.com>
> > wrote:
> > > ITA???s airline flight booking system, that was used by Orbitz and
> > > was pretty much entirely written in Common LISP, and it was certainly
> > > large and commercially successful. Orbitz was bought by Google for
> > > million. I don???t know how much of the LISP survived sustained
> attention by
> > > Google.
> > >
> > Google bought ITA, not Orbitz. Most of the logic in QPX is still in
> > Lisp, but it's not what you'd call "idiomatic" CL code. If one reads a
> > bunch of Paul Graham and Peter Norvig books and then gets onto QPX with
> > expectation of that sort of elegance, you end up pretty unhappy pretty
> > quick. They do a lot of things very differently to squeeze as much
> > performance as they can out of what has, historically speaking, been a
> > fairly mediocre compiler.
> Which is sort of my point. I don't know all the details but lisp and
> performance is not a thing.
That's a tad unfair.
It *can* be fast, it's just that the "Lisp" you're writing in that case
probably isn't the Lisp you wanted to be writing when you read about how
cool and elegant Lisp was: you're avoiding some constructs to prevent
boxing and unboxing arguments (e.g., put things inside of labels or flet's
instead of defun's or passing arbitrary lambdas around) or generating
useless garbage (don't cons up a list; setq the cdr) and favoring others
that are less elegant to get better object code out of the compiler.
If you can stomach the death-defying twists and turns from all the hoops
you have to jump through for all of that nonsense, then you can make it
fast -- but at the loss of the expressive advantage. But that trade-off
begs the question: why not write in a language that lets you write fast
(executing) code without jumping through hoops? That's a fair thing to ask
and most of the answers in Lisp's favor aren't particularly great.
- Dan C.
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