Re: The compilation approach in modern languages

On 28 Feb 2005 00:53:47 -0500, anton@mips.complang.tuwien.ac.at (Anton
Ertl) wrote:


>Ivan Boldyrev <boldyrev@cgitftp.uiggm.nsc.ru> writes:
>>> [Well, sure. Lots of languages can compile at runtime. -John]
>...
>>Perhaps, (Common) Lisp/Scheme is different from them because
>>COMPILE-FILE is *standard* function.
>
>Hmm, COMPILE-FILE is not quite what I consider compilation at
>run-time. Even in C I can do system("cc ..."); ok, some people have
>used that in combination with dlopen/dlsym to achieve a kind of
>run-time compilation, but it is relatively cumbersome.


Lisp has the standard function COMPILE for run-time compilation. It
also has COERCE which (among other uses) can create an interpreted
function at run-time from a suitably structured list.


When called directly on a suitable list, COMPILE calls COERCE to
create a function and then compiles and links the function.


COMPILE-FILE is merely a driver function for COMPILE which takes its
input from a stream.


>What I am thinking of when I hear Lisp and run-time compilation are
>things like macros and back-quote.


Most macro use in Lisp occurs at development time. The typical run
time use is to hot patch a running program and is hidden behind a LOAD
of the new code. A program whose normal operation requires a lot of
run time macro expansion is either doing something incredibly smart or
insanely stupid.


George

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