Re: 5.1 RTL macros

[David Jones <drj@...>]

On Apr 05, 2006, at 14:05, Lisa Parratt wrote:

> David Jones wrote:
> > It's often useful in lexing.  The functionality of ungetc will always 
> > be needed, and I think that's unavoidable.  So if it didn't exist 
> > then lots of programs would end up implementing their own version of 
> > Standard C IO streams, but with one byte of pushback.
>
> Meh - few excuses that still hold in this day and age for not 
> buffering in memory before processing, imho.

Well, implementing ones own buffering is less-efficient, error prone, 
and not always simple.  How do I decide which bit to buffer?  Is my 
buffer a single array, in which case how do I arrange access to 
previous bytes (like ungetc) without copying; or is it multiple arrays, 
in which case how do I provide a natural access to the bytes within it?

In fact I think C is increasingly deployed in smaller and smaller 
devices.  The 8-bit microcontrollers are growing up to a point where 
they can feasibly implement a reasonable approximation to C.  The 
desktop and server machines are so fast that people are switching away 
from C and to languages like Python for interactive GUIs.

Personally, if I'm programming for a system that's big enough to 
implement mmap() (or equivalent) then I probably want to be using 
Python, not C.  Conversely, if I'm using C, I'm not likely to be on a 
very big system and I probably do want to look after my bytes.

> > I'm curious as to why you don't like it so much.  Is it buggy vendor 
> > implementations? Non-portable C code that relied on more than one 
> > byte of ungetc? Having to implement a C-like stream interface on top 
> > of an abstraction that didn't provide anything like ungetc? Or 
> > something else?
>
> All of the above. It also adds a special case when coding 
> implementations - makes the code fugly imho.

So in a world where ungetc didn't exist, do you think the two uses of 
it in lua would be made any simpler?  Because one has to weigh up the 
ugliness of a support library against the ugliness of applications 
using that library.

drj