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Posted by ZeldorBlat on 05/07/07 18:08
On May 7, 1:21 pm, Rami Elomaa <rami.elo...@gmail.com> wrote:
> ZeldorBlat kirjoitti:
>
>
>
> > On May 7, 11:05 am, dennis.spreng...@gmail.com wrote:
> >> Consider the following multi-dimensional array:
> >> ---------------------------
> >> $arr = array(
> >> array(3, 5, 7, 9),
> >> array(2, 4, 6, 8),
> >> array(1, 3, 5, 7)
> >> );
>
> >> function add_arrays($arr) {
> >> for ($row = 0; $row < count($arr[0]); $row++) {
> >> for ($column = 0; $column < count($arr[$column]); $column++) {
> >> $totals[$row] = $totals[$row] + $arr[$column][$row];
> >> }
> >> }
> >> print_r($totals);
>
> >> }
>
> >> add_arrays($arr);
> >> ---------------------------
> >> This returns the following array:
> >> Array ( [0] => 6 [1] => 12 [2] => 18 [3] => 24 )
>
> >> These are the totals of the array's in $arr: 6 (3 + 2 + 1, added all
> >> first elements), 12 (5 + 4 + 3, added all second elements), etc. This
> >> took me quite a portion of the day to construct ;) However, I would
> >> like add_arrays to return a multidimensional array like this:
>
> >> Array (
> >> Array ( [0] => 3 [1] => 5 [2] => 7 [3] => 9 ) // 1st row
> >> Array ( [0] => 5 [1] => 9 [2] => 13 [3] => 17 ) // 1st row + second
> >> row (i.e. 5 = 3 + 2)
> >> Array ( [0] => 6 [1] => 12 [2] => 18 [3] => 24 ) // 1st _ 2nd + 3rd
> >> row (i.e. 6 = 3 + 2 + 1)
> >> )
>
> >> Could somebody please help me building a function that does just that?
> >> Adding one row to the previous one and adding the result to the output
> >> array? Any help would be greatly apprectiated!
>
> > Here's one way. Obviously there are others, also.
>
> > function add_arrays_cumulative($arr) {
> > $out = array();
>
> > for($i = 0; $i < count($arr); $i++) {
>
> This is hair-splitting, but since count($arr) is static, it would save
> some cpu cycles to store it in a variable instead of calling count() on
> each iteration:
>
> for($i = 0, $limit=count($arr); $i < $limit ; $i++) {
>
> Or better yet, iterate the array with foreach:
>
> foreach($arr as $i => $row) {
>
> > if(!isset($out[$i]))
> > $out[$i] = array();
>
> > for($j = 0; $j < count($arr[$i]); $j++)
>
> Same goes here.
>
> I've gotten so used to foreach that I'm missing it a lot when I'm using
> a language that hasn't got such a structure... It's so convinient.
>
> --
> Rami.Elo...@gmail.com
>
> "Wikipedia on vähän niinq internetin raamattu, kukaan ei pohjimmiltaan
> usko siihen ja kukaan ei tiedä mikä pitää paikkansa." -- z00ze
Yes -- you're correct on both. In the normal course of things I would
save the value of count() and also use a foreach instead. Using
count() over and over again makes it a bit easier to follow the code,
and the OP was using regular for loops so I stuck with those.
In practice I use foreach almost exclusively -- and you're right in
that I really miss it in other languages :)
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