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While, for, foreach or something else to loop.

Newcomers to programming often ask "which loop should I use?"

Every language has a while loop, most have a for loop (though sometimes those differ in what they do - Python is an exceptional one, for example), and many have a foreach loop. Then you get the odd ones such as the until loop in Perl ...

A while loop is at the "lowest level" - you can always do what you want with that, but it may be a bit wordier than you wish in coding, and that may make it a bit more prone to coding with errors ("bugs"), and it may make it harder for someone coming along later to update your code to understand what's going on.

On yesterday's PHP course, I took an example of an array that I wanted to print our element by element ...

Using a while loop, I have separate statements to set the position number in the array that I'm starting at, to check the end, and to step up the counter (to the array) by one:

  $at = 0;
  while ($at < count($info)) {
    print "w: $info[$at]\n";
    $at++;
    }


With a for loop, I take my initial position setter and my stepper and move them into the controlling for statement, making the code much easier to follow, but not really reducing the code elements:

  for ($at = 0; $at < count($info); $at++) {
    print "f: $info[$at]\n";
    }


If I don't need to know the position number (don't want to print it out, or look back to the "previous", forward to the "next", then I can do completely without the position variable (called $at in my example) using a foreach loop:

  foreach ($info as $fruit) {
    print "g: $fruit\n";
    }


Complete example - [here]. PHP courses - [here].
(written 2012-11-06, updated 2012-11-10)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H104 - PHP - Control Statements
  [4323] Learning to program - Loop statements such as while - (2014-11-22)
  [4322] Learning to Program - the conditional statement (if) - (2014-11-21)
  [3895] Flowchart to program - learning to program with Well House - (2012-10-14)
  [3397] Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18)
  [3200] How a for loop works Java, Perl and other languages - (2011-03-12)
  [2912] Predictions for the seagull population - (2010-08-09)
  [2304] Extracting real data from an exported file in PHP or Perl - (2009-07-25)
  [1825] Question Mark - Colon operator (Perl and PHP) - (2008-10-08)
  [1696] Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04)
  [1477] Decisions - small ones, or big ones? - (2007-12-18)
  [1220] for loop - how it works (Perl, PHP, Java, C, etc) - (2007-06-06)
  [1199] Testing for one of a list of values. - (2007-05-22)
  [1191] Smart English Output - via PHP and Perl ? : operator - (2007-05-18)
  [962] Breaking a loop - Ruby and other languages - (2006-12-03)
  [863] Double and Triple equals operator in PHP - (2006-09-12)
  [657] The ternary operator in Python - (2006-03-25)
  [421] Don't repeat code - use loops or functions - (2005-08-21)
  [406] Assignment, equality and identity in PHP - (2005-08-08)
  [353] Wimbledon Neck - (2005-06-20)
  [340] Code and code maintainance efficiency - (2005-06-08)

P206 - Perl - More Loops and Conditionals
  [3619] Ruby v Perl - a comparison example - (2012-02-21)
  [3398] Perl - making best use of the flexibility, but also using good coding standards - (2011-08-19)
  [2972] Some more advanced Perl examples from a recent course - (2010-09-27)
  [2967] Multiway branches in Perl - the given and when syntax - (2010-09-22)
  [2892] Alternative loops and conditionals in Ruby and Perl - (2010-07-28)
  [2832] Are you learning Perl? Some more examples for you! - (2010-06-27)
  [2824] A pint of Black Rat, and a lazy barman - (2010-06-25)
  [2817] Setting a safety net or fallback value in Perl - (2010-06-19)
  [2815] switch and case, or given and when in Perl - (2010-06-17)
  [2711] For loop - checked once, or evety time? Ruby v Perl comparison and contrast - (2010-04-07)
  [1582] Ruby, C, Java and more - getting out of loops - (2008-03-19)
  [299] What - no switch or case statement? - (2005-05-03)
  [138] Perl - redo and last without a loop - (2004-12-02)


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