How To Decide when to use a loop

Logan · 05-14-2009, 09:28 AM

I'm writing an informal test on programming basics on Monday (18 May), and I need to know (but can't find anything) how do you decide when to use what type of loop?

How do you decide you need a for..next loop, or a for each..next, or a while...wend loop?

I've always just thought "OK, I need it to do this while the recordset is still open, so a while loop should do"

Any answers or links you can post will be really appreciated.

conor · 05-14-2009, 01:10 PM

Well in PHP anyway this is what I do.

Use a while loop when you want to say "while something equals something else do this". Fpr example this while loop keeps executing until this function returns true:

Code:

function getValue(){
    // blah blah blah
    if($blah!=$ahh) return false;
    return true;
}

$val=getValue();

while($val==false){
   echo 'returned false <br/>';
}

or you could use it for a database query. This statement continues until all the rows in the database have been cycled through:

Code:

$query=mysql_query('select * from pages');

while($r=mysql_fetch_array($query)){
   echo 'row: '.$r.'<br/>';
}

You use a for each statement if you want to do something like cycling through an array. For example this code will cycle three times:

Code:

$array=array( 1=>'one',2=>'two',3=>'three' );

foreach($array as $k=>$v){
   echo 'Num: '.$k.' or '.$v.'<br/>';
}

And finally you use a for statement when you want to repeat something a specific number of times. This example will repeat 10 times:

Code:

$num=10;

for($i=0;$i<=$num;$i++;){
   echo $num.'<br/>';
}

05-14-2009, 09:28 AM	#1
Logan Bronze Member Join Date: Apr 2009 Posts: 25	How To Decide when to use a loop I'm writing an informal test on programming basics on Monday (18 May), and I need to know (but can't find anything) how do you decide when to use what type of loop? How do you decide you need a for..next loop, or a for each..next, or a while...wend loop? I've always just thought "OK, I need it to do this while the recordset is still open, so a while loop should do" Any answers or links you can post will be really appreciated.

05-14-2009, 01:10 PM	#2
conor Gold Member Join Date: Oct 2008 Location: Ireland Posts: 349	Well in PHP anyway this is what I do. Use a while loop when you want to say "while something equals something else do this". Fpr example this while loop keeps executing until this function returns true: Code: function getValue(){ // blah blah blah if($blah!=$ahh) return false; return true; } $val=getValue(); while($val==false){ echo 'returned false <br/>'; } or you could use it for a database query. This statement continues until all the rows in the database have been cycled through: Code: $query=mysql_query('select * from pages'); while($r=mysql_fetch_array($query)){ echo 'row: '.$r.'<br/>'; } You use a for each statement if you want to do something like cycling through an array. For example this code will cycle three times: Code: $array=array( 1=>'one',2=>'two',3=>'three' ); foreach($array as $k=>$v){ echo 'Num: '.$k.' or '.$v.'<br/>'; } And finally you use a for statement when you want to repeat something a specific number of times. This example will repeat 10 times: Code: $num=10; for($i=0;$i<=$num;$i++;){ echo $num.'<br/>'; } __________________ Conor

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