On 17 Jan 2008, at 10:56 am, Peter Verswyvelen wrote:
You're talking about O(big)... But wasn't the C language in some way
succesful because on the hardware at that time other much nicer
languages (e.g. LISP) were just way too slow? Or was this just O(n)
times slower?
No. C was designed as a Systems Implementation Language (there were
lots of
SILs) with the following advantages:
(1) tolerable code from a fairly naive compiler (the PDP-11 UNIX V7 C
compiler
did a little optimisation, but not very much; function entry/
exit was done
using calls to library support routines in order to save space,
so every
function call involved *three* hardware-level function calls; I
speeded up
a text editor by about 20% by replacing just two tiny functions
by hand-
written assembler, and it was this function call overhead that
was saved)
(2) tolerably compact code; a fairly useful library of stuff that you
didn't
actually have to use (again, said text editor got a notable
space saving
by *not* using any C stdio stuff at all, not using any floating
point stuff
at all, and not even linking, let alone calling, malloc())
(3) fairly direct mapping between language and machine so the
"performance model"
you had to keep in your head was simple
(4) a fair degree of portability between compilers (although the PC
world
spoiled this to some extent).
Lisp *performance* compared with C was always O(1) and sometimes
excellent;
I have had Scheme code running faster than C. It was the memory
footprint
caused by Lisp's comparatively large library (possibly even including
the
compiler) always being there in full, and the (largely imaginary)
cost of
garbage collection which scared people off. It is intensely annoying
to an
old Lisp hacker to see Java succeeding despite being worse at just about
everything Lisp was ever criticised for. But in fairness, the other
thing was
that before the advent of Common Lisp, every Lisp was different.
Develop in
MacLisp and you could forget about delivering in Interlisp, and vice
versa.
This is why, although I actually have Lazy ML on my machine still, I
dropped
it for Haskell.
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