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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.arch
Subject: Re: Self-modifying code
Message-ID: <6516@utzoo.UUCP>
Date: Sat, 15-Mar-86 21:00:33 EST
Article-I.D.: utzoo.6516
Posted: Sat Mar 15 21:00:33 1986
Date-Received: Sat, 15-Mar-86 21:00:33 EST
References: <546@tekcrl.UUCP> <5100019@ccvaxa>, <4254@dartvax.UUCP>
Organization: U of Toronto Zoology
Lines: 19

> > For some specific instance of a general routine with all sorts of
> > ifs depending on parameters values, take a general prototype with all
> > the ifs in it, compile only the parts you need into a buffer, and then
> > execute that buffer.
> 
> How does this differ (conceptually) from invoking a subroutine which has 
> its own local memory and passing it parameters?

Conceptually, not at all.  Practically, quite a bit.  Making choices during
compilation is generally faster than making them at run time.  If the code
is going to be used enough to justify the compilation overhead, compiling
will be a considerable win.  It also gives you access to a huge number of
different alternatives without having to write, compile, and store all of
them in advance.  (If you don't think this is significant, try enumerating
the different cases of something like an efficient BitBlt implementation.
Thousands of different code sequences.)
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry