On Dec 11, 2006, at 3:12 PM, Theodore H. Smith wrote:
From: Charles Yeomans <[EMAIL PROTECTED]>
Date: Sun, 10 Dec 2006 16:38:46 -0500
On Dec 10, 2006, at 12:40 PM, Theodore H. Smith wrote:
From: William Squires <[EMAIL PROTECTED]>
Date: Sat, 9 Dec 2006 18:54:23 -0600
Oops, I guess I misread the intent of the original line; I
thought
you were just checking to see if the line could be a number, and
were
interested in a more efficient way to quickly test it without a lot
of overhead. And, actually, the 'quickie' test with Asc will even
allow you to put comments after the number in the file, whereas the
original call to IsNumber() would - I believe - fail if there were
extra non-numeric characters after the 1st numeric character, so:
1 // <- translates to 'Case 1'
would pass with the Asc() test, but would fail on the IsNumber()
test
(I think - I haven't actually tried it myself.) Of course, I didn't
try the perl test either; not being a perl fan myself.
Granted, this approach, while allowing comments, doesn't
necessarily define what the comment character is!
With ElfData, the code would be:
if line.OutCharSet(numbers) = 0 then
// it's a number
else
// text
end
It's actually quite simple code.
the "numbers" variable, you init earlier, like this:
numbers = "0123456789"
This creates a 256 byte lookup table in RAM, making for scanning of
strings of any character set, very fast.
The same approach is possible with REALbasic, but it won't have C
compiler optimisations, and will have a lot of method call overhead.
Why is that? I've always found array access to be reasonably fast.
Well, it will be fast, but not that fast.
It should take 1 instruction to read a byte from a string and
increment the pointer.
It should take 1 more instruction to load the boolean from the
table using the byte as the lookup index.
So that's 2 instructions to get the bool.
I think REALbasic will take more than 2 instructions to do
something like this:
dim b as boolean
b = MyArray( ascb( midb( s, i, 1 ) ) )
Maybe more like 500 instructions.
Perhaps, but I wouldn't do it that way.
Charles Yeomans
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