Which is better practice - for loop with break or conditional loop?

Asked 2009-02-27T17:03:59.383

I'm just curious what peoples' thoughts are on this topic. Let's say I have an Array of Objects, and I want to loop through them to see if the Objects contain certain values, and if so, I want to stop the loop. Which is better practice - a for loop with a break, or a conditional loop?

The pseudo-code in the example I have provided is for argument's sake only (it is also in ActionScript, since that is my primary language of late). Also, I am not looking for best practice ideas on syntax.

for loop with break:

var i:int;

var isBaxterInMilwaukee:Boolean;    

for (i = 0; i < arrayLen; i++)
{
    if (myArray[i]["name"] == "baxter"
         && myArray[i]["location"] == "milwaukee")
    {
        isBaxterInMilwaukee = true;

        barkTwice();

        break;
    }
}

conditional loop:

var i:int;

var isBaxterInMilwaukee:Boolean;    

while (!isBaxterInMilwaukee && i < arrayLen)
{
    if (myArray[i]["name"] == "baxter"
         && myArray[i]["location"] == "milwaukee")
    {
        isBaxterInMilwaukee = true;

        barkTwice();
    }

    i++;
}

Edit Report

2 Answers

In short, you should go with whichever version is the easiest to read and maintain.

In slightly older times, I know breaking out of a loop was considered to be a no-no (on par with a goto statement). Loops were supposed to break on the loop condition and nowhere else. Thus, the while-loop would have been the way to go.

(This is probably a holdover from assembly, where loops are basically a block of code with a go-to-the-beginning-if-true jump statement at the end. Multiple conditional-jump statements in the block make it exceedingly hard to debug; thus they were to be avoided and combined into one at the end.)

I feel this idea seems to be changing a bit today, especially with foreach loops and the managed world; it's really a matter of style now. Break-on-found for-loops have perhaps come to be acceptable to many, save some purists of course. Note that I would still avoid using break in a while-loop, however, as this can muddle the loop condition and make it confusing.

If you'll allow me to use a foreach loop, I consider the code below to be a lot easier to read than its while-loop brother:

bool isBaxterInMilwaukee;    

foreach (var item in myArray)
{
    if (item.name == "baxter" && item.location == "milwaukee")
    {
        isBaxterInMilwaukee = true;    
        barkTwice();
        break;
    }
}

However, as the logic grows in complexity, you may want to consider a prominent comment near the break statement lest it become buried and hard to find.

Arguably, this whole thing should be refactored into its own function which doesn't break on found, but actually returns the result (feel free to use the for-loop version instead):

bool isBaxterInMilwaukee(Array myArray)
{      
    foreach (var item in myArray)
    {
        if (item.name == "baxter" && item.location ==


                        
                        
                            answered 2009-02-27T17:18:45.883


            
            
                
                    
                        
                            
                            
                        
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                        I would definitely go with the for+break. The ‘for’ is an instantly-recognisable idiom for “iterate over sequence” and it's easier to understand “iterate over sequence; end early if value found” than the combined loop-and-stop condition.

There may be evidence for this in the way you seem to have made two mistakes in your conditional loop code!


the while condition (!isBaxterInMilwaukee || i == arrayLen) — did you mean “(!(isBaxterInMilwaukee || i == arrayLen))”?
break statement is unnecessary if you're using a terminate-loop variable.


Personally I find a simple ‘break’ much easier to read than trying to track a terminate-loop variable.

                        
                        
                            answered 2009-02-27T17:37:18.227



        
        
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