On Sat, 20 Feb 2010 17:44:00 -0500, you wrote:
On Sat, Feb 20, 2010 at 11:10 AM, Nathan Rixham nrix...@gmail.com wrote:
Richard Quadling wrote:
On 20 February 2010 11:18, clanc...@cybec.com.au wrote:
Or:
$a = array ('Cats', 'white', 'Dogs', 'black', 'Mice', 'grey', 'Camels',
'brown');
$b = '';// Just in case it has some
leftover value
$k = 2* (int) (count ($a)/2); // ensure even no of terms
$i = 0; while ($i $k)
{
$b[$a[$i++]] = $a[$i++]; // ***
}
And this works:
$i = 0; $k = array_keys($b);
while ($i count($b)) {echo 'h5'.$i.': '.$k[$i].' = '.
$b[$k[$i++]].'/h5'; }
0: Cats = white
1: Dogs = black
2: Mice = grey
3: Camels = brown
( *** I have always been wary of using statements like this because I
was unsure when the
incrementing would occur, so I tried it.)
Clancy
?php
$i = 10;
echo $i++; // Shows 10 and $i becomes 11
echo ++$i; // $i becomes 12 and 12 is shown.
?
Post increment and pre increment.
No need to be wary of them.
http://docs.php.net/manual/en/language.operators.increment.php
Expanding on what Richard says; there does seem to be a growing number
of people who haven't stopped to learn the very basics of PHP (or
languages in general).
I'd strongly recommend that all those in doubt over the basics take a
few hours out to (re-)familiarise themselves; and there's no finer
resource to do this than the php manual [1]
You'll notice the manual goes as follows:
# Basic syntax
# Types
# Variables
# Constants
# Expressions
# Operators
# Control Structures
# Functions
... more
And that's the order in which you should learn; in short you can't
really program or script without knowing basics through control structures.
Do hope this mail doesn't sound condescending in any way; as it's meant
with the best intentions and really will make you're (working) life a
lot easier. I myself still refer back to these base sections
periodically, and every time I do - a new detail pops out that makes
something easier.
[1] http://docs.php.net/manual/en/langref.php
Many Regards,
Nathan
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Clarifying what Clancy specifically said:
( *** I have always been wary of using statements like this because I was
unsure when the
incrementing would occur, so I tried it.)
The asterisks inform us he was speaking about the first example, and the
language informs us he was speaking about the statement, not the increment
operator, itself.
$b[$a[$i++]] = $a[$i++]; // ***
It's actually quite a clever implementation of the algorithm request that
prompted this thread, and because of it's uniqueness, (incrementing a
variable multiple times within the same statement on both sides of the '='),
I don't this reflects that Clancy stopped to learn the very basics of PHP.
Actually, Clancy taking the time to try something to better learn the
language (just for the sake of coding fun, no less) reflects the desire to
learn new things, and that's exactly the type of person I hope is drawn to
the PHP community.
Thanks for the example, Clancy :)
Adam
Thanks, Adam.
I started programming before there were any manuals (or classes), and I had to
jump in at
the deep end. I do like to know how things work, but the days when you could
make your own
complete commented disassembly of the operating system (as I did for CP/M) are
long since
gone, and it is no longer possible for any single person to have even a
reasonable working
knowledge of how all the programs on his computer operate. I regret I have to
admit that
it is now beyond me to have a working familiarity even with the programs I need
for
webpage design -- PHP, HTML, CSS and Javascript, let alone trying to throw in
C++, Apache
Unix. Also questions like this tend to come up when I'm in the middle of
implementing
something complicated, so usually I take the easy way out, instead of taking
the time off
to try to answer the question.
The particular case which prompted my comment was the one where you want to
copy part of
one array into the corresponding elements of another array. Should you write:
$i = 0; $j=count($a); while ($i $j) { $b[$i] = $a[$i++]; }OR
$i = 0; $j=count($a); while ($i $j) { $b[$i++] = $a[$i]; }
Surprisingly (to me) the answer is neither. (Assuming $j = 5) the first gives
$b[1] =
$a[0], with $b[0] undefined, while the second gives $b[0] = $a[1], with $b[4]
undefined.
Experiment shows that you can either be safe, as I have always done, and write:
$i = 0; $j=count($a); while ($i $j) { $b[$i] = $a[$i]; ++$i; }
or you can write:
$i = -1; $j=count($a) - 1; while ($i $j) { $b[++$i] = $a[$i]; }
This seemed moderately logical, but then I found you can also write:
$i = -1; $j=count($a) - 1; while ($i $j) { $b[$i] = $a[++$i]; }
I think I will stick to the safe way!
--
