For loop if statement issue

Question

I have a for loop and inside of it I have a if statement something like this:

  $output = "";
  $limit = 550;
  for ($i = 1; $i <= $limit; $i++) {
    if($i < 10){
     $output .= my_function($i*1);
    }elseif($i < 20){
     $output .= my_function($i*2);
    }elseif($i < 30){
     $output .= my_function($i*3);
    }
    //elseif 30 => 550
  }

Problem is I find it very tedious to have to continue this elseif statement down to 550. Is there any way to do this without writing 55 elseif statements.

$output = my_function($i * ceil(($i+1)/10));? Apart from that: Is $output used in the loop or just outside? — Nobody moving away from SE
– Nobody moving away from SE, Commented Aug 21, 2011 at 14:30
Ok and the i in the function parameters should be $i right? — Nobody moving away from SE
– Nobody moving away from SE, Commented Aug 21, 2011 at 14:34

Evan Mulawski · Accepted Answer · 2011-08-21 14:29:38Z

9

Your thinking is exactly right. Having to repeat that much code is a sure sign that something is off.

In this case, the solution is pretty simple. You just want to use integer division to knock off the ones digit, which you don't care about. You also need to adjust by one since you're checking less than and not less than or equal.

$output = "";
$limit = 550;
for ($i = 1; $i <= $limit; $i++) {
     $temp = (int) ($i / 10) + 1;
     $output = my_function($i*$temp);
}

edited Aug 21, 2011 at 14:29

Evan Mulawski

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answered Aug 21, 2011 at 14:24

Jeremy

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1 Comment

Bojangles Over a year ago

+1 for actually giving an explanation with your answer. We need to see more like this!

phihag · Accepted Answer · 2011-08-21 14:21:50Z

0

for ($i = 1;$i <= 550;$i++) {
  $multiplier = (int) ($i / 10) + 1;
  $output = my_function($i * $multiplier); 
}

answered Aug 21, 2011 at 14:21

phihag

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Comments

David Thomas · Accepted Answer · 2011-08-21 14:22:34Z

0

My first thought is that you could use:

  $output = "";
  $c = 0;
  $limit = 550;
  for ($i = 1; $i <= $limit; $i++) {
    if (($i + 1) % 10 == 0) {
        $c++;
        $output = my_function($i*$c);
    }
  }

answered Aug 21, 2011 at 14:22

David Thomas

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1 Comment

phihag Over a year ago

That works, but is hard to read and tends to fail. I think recalculating $c in the loop is preferable to blowing up the state space with it.

Ash Burlaczenko · Accepted Answer · 2011-08-21 14:23:39Z

0

How about

$output = "";   
$limit = 550;   

for ($i = 1; $i <= $limit; $i++) {     
    $num = ($i / 10) + 1      
    $output = my_function($i*$num);
}

answered Aug 21, 2011 at 14:23

Ash Burlaczenko

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1 Comment

phihag Over a year ago

php's default division is floating-point. Therefore, num will be 1.1 in the first iteration, not 1.

Roman Pietrzak · Accepted Answer · 2011-08-21 14:25:17Z

0

Try this:

$output = "";
$limit = 550;
for ($i = 1; $i <= $limit; $i++)
{
    $output = my_function($i * (1 + (int)($i / 10)));
}

answered Aug 21, 2011 at 14:25

Roman Pietrzak

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Comments

Peter · Accepted Answer · 2011-08-21 14:33:14Z

0

The solution should be as simple as the following:

$output = "";
$limit = 550;
for ($i = 1; $i <= $limit; $i++)
{
    $num = ceil($i/10);
    $output = my_function($num, $num-1);
}

hmm the original code seems to have changed since I started typing this. The my_function function now only has 1 input when it originally had 2.

answered Aug 21, 2011 at 14:33

Peter

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Comments

RiaD · Accepted Answer · 2011-08-21 14:34:55Z

0

for ($i = 1; $i <= $limit; $i++) {
     $output = my_function(i*floor($i/10+1));
}

Point is not really about this question:
You reassign output on every loop iteration, but only last will be vailable after loop? Need you $output[]= or $output.= ?

answered Aug 21, 2011 at 14:34

RiaD

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