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Re: Learning to code by reading code

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"BartC" <bc@freeuk.com> wrote in message news:jhvtig$fam$1@dont-email.me...
> "Rod Pemberton" <do_not_have@noavailemail.cmm> wrote in message
> news:jhvobn$ujr$1@speranza.aioe.org...
...

> > There are two fundamental problems with interpreters that
>> can't be overcome: 1) they reimplement the mechanisms of
> > assembly language which slows things down alot
>
> An interpreter may well be *implemented* in assembly language.

That's typical.

> Every instruction that the interpreter deals with could be implemented
> by a carefully hand-crafted and optimised block of assembly code!

So?  An interpreter still reimplements for a virtual machine what native
assembly already does, i.e., slower.

> Sometimes better than automatically compiled code.

The "hand" optimized sequences for interpreters are much smaller than what a
compiler usually optimizes.  So, while the small pieces might be optimized
better, overall the larger compiler pieces are better optimized.

> >  2) they can't optimize and compile code sequences which
> > dramatically slows down loops and other control-flow.
>
> Tell that to the guy who implemented the LuaJIT interpreter. Numeric
> benchmarks are often faster than optimised C!
>

Well, tell him JIT is not an interpreter:
http://en.wikipedia.org/wiki/Just-in-time_compilation

> C is pretty good, but it has to spend a lot of time recognising constructs
> in the source code [which] could be expressed directly in a higher level
> language and which can be executed directly (vector operations for
> example). It doesn't always manage to do that.

Those constructs must still be converted to assembly.  So, even if you can
"express them directly", what real advantage is that?  They have to be
converted to the underlying assembly language no matter what.  If you're
looking for "short-hand" to express "missing" some constructs, use some
integers and an array ...

> And if implementing something unusual, you can often write almost directly
> from pseudo-code in a higher level language, but a quick, throwaway
> implementation in C may well be slower; you need to spend time with C in
> achieving what's already been done inside the interpreter.
...


Rod Pemberton

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Re: Learning to code by reading code (was: The way to read STL source code) "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-18 19:00 -0500
  Re: Learning to code by reading code "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-18 22:34 -0600
  Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-19 03:54 -0500
    Re: Learning to code by reading code "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-02-19 10:42 +0100
      Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-19 22:34 +0000
        Re: Learning to code by reading code "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-02-20 12:22 +0100
    Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-20 03:39 -0500
  Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-19 03:54 -0500
    Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-19 08:40 -0800
      Re: Learning to code by reading code "MikeWhy" <boat042-nospam@yahoo.com> - 2012-02-19 13:17 -0600
        Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 02:32 -0800
          Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-20 13:02 +0100
            Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 05:09 -0800
              Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-20 15:11 +0100
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 07:39 -0800
      Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-20 04:14 -0500
        Re: Learning to code by reading code "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-02-20 11:14 +0100
          Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 05:13 -0800
        Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 02:49 -0800
          Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-20 13:02 +0100
            Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-20 05:18 -0800
              Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-20 13:53 +0000
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-21 01:32 -0800
                Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-21 16:16 +0100
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-21 08:40 -0800
          Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-20 17:36 -0500
            Re: Learning to code by reading code Dombo <dombo@disposable.invalid> - 2012-02-21 00:45 +0100
              Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-21 04:35 -0500
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-21 08:48 -0800
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-22 00:12 -0800
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-22 06:12 -0500
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-22 04:30 -0800
                Re: Learning to code by reading code Geoff <geoff@invalid.invalid> - 2012-02-22 10:45 -0800
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-23 01:12 -0800
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-23 07:34 -0500
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-23 05:46 -0800
                Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-24 08:38 +0100
                Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-24 08:40 +0100
                Re: Learning to code by reading code "io_x" <a@b.c.invalid> - 2012-02-24 09:38 +0100
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-25 05:25 -0500
                Re: Learning to code by reading code Dombo <dombo@disposable.invalid> - 2012-02-25 12:50 +0100
                Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-25 06:13 -0800
                Re: Learning to code by reading code Gareth Owen <gwowen@gmail.com> - 2012-02-26 07:20 +0000
            Re: Learning to code by reading code Juha Nieminen <nospam@thanks.invalid> - 2012-02-21 08:23 +0000
              Re: Learning to code by reading code Juha Nieminen <nospam@thanks.invalid> - 2012-02-21 08:43 +0000
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-21 04:47 -0500
                Re: Learning to code by reading code Juha Nieminen <nospam@thanks.invalid> - 2012-02-21 10:09 +0000
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-22 05:38 -0500
              Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-21 04:31 -0500
                Re: Learning to code by reading code Juha Nieminen <nospam@thanks.invalid> - 2012-02-21 10:05 +0000
                Re: Learning to code by reading code "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-02-21 12:21 +0100
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-22 06:04 -0500
                Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-21 11:01 +0000
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-22 05:59 -0500
                Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-22 12:59 +0000
                Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-23 07:03 -0500
                Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-24 14:20 +0000
            Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-21 01:27 -0800
        Re: Learning to code by reading code Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2012-02-20 22:25 +0100
          Re: Learning to code by reading code Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-02-26 08:47 +0000
            Re: Learning to code by reading code "BartC" <bc@freeuk.com> - 2012-02-26 10:55 +0000
        Re: Learning to code by reading code Nomen Nescio <nobody@dizum.com> - 2012-02-22 08:59 +0100
          Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-22 05:59 -0500
            Re: Learning to code by reading code Nomen Nescio <nobody@dizum.com> - 2012-02-22 13:47 +0100
              Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-23 06:21 -0500
        Re: Learning to code by reading code Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-02-22 00:08 -0800
  Re: Learning to code by reading code "Rod Pemberton" <do_not_have@noavailemail.cmm> - 2012-02-19 03:54 -0500
  Re: Learning to code by reading code Marco van de Voort <marcov@toad.stack.nl> - 2012-02-19 11:27 +0000

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