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- Subject: Re: 5.1 RTL macros
- From: David Jones <drj@...>
- Date: Wed, 5 Apr 2006 15:17:31 +0100
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
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.