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Posted by Osiris on 12/02/07 08:07
On Sat, 01 Dec 2007 09:36:47 -0500, Jerry Stuckle wrote:
> Osiris wrote:
>> Just something I would like to share:
>>
>> I just learned the hard way (2 days detective work on a bug) that foreach
>> loops are not at all like for loops, not intuitive at all. BEWARE: arrays
>> and matrices are sparse by design/definition in PHP.
>>
>> I'm doing some matrix manipulation in a Finite Element program.
>> Translating Fortran to PHP, because hosters won't allow anything else
>> than PHP.
>> I wish PHP would do array and matrix stuff like Fortran or C, btw.
>> Something for PHP 6 ?
>> Check out this code:
>>
>> $k = array(1=>
>> array(1=>1,1,1,1,1,1),
>> array(2=>1,1,1,1,1),
>> array(3=>1,1,1,1),
>> array(4=>1,1,1),
>> array(5=>1,1),
>> array(6=>1));
>>
>> /*
>
> I find foreach loops to be quite intuitive. However, your FORTRAN
> naming conventions make your code very hard to understand, and I don't
> have the time to try to figure out what you're trying to do.
>
> Try using some descriptive names for your variables. It will make your
> code a lot easier to understand.
>
There is nothing to describe , really... this example is just about a
general matrix with numbers to be mirrored.
The issue here is, that in a foreach loop you can inadvertedly enter extra
coefficients in the matrix, that are processed in a next iteration.
A for loop determins exactly which coefficients to process. A foreach loop
processes all that it encounters, new or old.
Mind you: I know what the problem is with the code. I did not say PHP was
in error, just that foreach-es are not alway what you EXPECT them to
be.
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