Is it a bad practice to use break in a for loop

Question

Is it a bad practice to use break statement inside a for loop   Say  I am searching for an value in an array  Compare inside a for loop and when value is found  break  to exit the for loop   Is this a bad practice  I have seen the alternative used  define a variable vFound and set it to true when the value is found and check vFound in the for statement condition  But is it necessary to create a new variable just for this purpose   I am asking in the context of a normal C or C   for loop   P S  The MISRA coding guidelines advise against using break

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On MISRA 98 rules  that is used on my company in C dev  break statement shall not be used     Edit   Break is  allowed in MISRA  04

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I disagree   Why would you ignore the built-in functionality of a for loop to make your own  You do not need to reinvent the wheel   I think it makes more sense to have your checks at the top of your for loop like so  for int i   0  i  lt  myCollection Length  amp  amp  myCollection i  SomeValue     Break Condition   i        loop body     or if you need to process the row first  for int i   0  i  lt  myCollection Length  amp  amp   i    0   true   myCollection i-1  SomeValue     Break Condition    i        loop body     This way you can write a function to perform everything and make much cleaner code    for int i   0  i  lt  myCollection Length  amp  amp   i    0   true   myCollection i-1  SomeValue     Break Condition    i          DoAllThatCrazyStuff myCollection i        Or if your condition is complicated you can move that code out too   for int i   0  i  lt  myCollection Length  amp  amp  BreakFunctionCheck i  myCollection   i          DoAllThatCrazyStuff myCollection i         Professional Code  that is riddled with breaks doesn t really sound like professional code to me  It sounds like lazy coding

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There is nothing inherently wrong with using a break statement but nested loops can get confusing   To improve readability many languages  at least Java does  support breaking to labels which will greatly improve readability   int   iArray   new int   0 1 2 3 4 5 6 7 8 9   int   jArray   new int   0 1 2 3 4 5 6 7 8 9       label for i loop iLoop  for  int i   0  i  lt  iArray length  i              label for j loop     jLoop  for  int j   0  j  lt  jArray length  j               if iArray i   lt  jArray j                   break i and j loops             break iLoop            else if  iArray i   gt  jArray j                     breaks only j loop             break jLoop            else                  unclear which loop is ending                 breaks only the j loop              break                      I will say that break  and return  statements often increase cyclomatic complexity which makes it harder to prove code is doing the correct thing in all cases     If you re considering using a break while iterating over a sequence for some particular item  you might want to reconsider the data structure used to hold your data   Using something like a Set or Map may provide better results

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Depends on your use case  There are applications where the runtime of a for loop needs to be constant  e g  to satisfy some timing constraints  or to hide your data internals from timing based attacks    In those cases it will even make sense to set a flag and only check the flag value AFTER all the for loop iterations have actually run  Of course  all the for loop iterations need to run code that still takes about the same time   If you do not care about the run time    use break  and continue  to make the code easier to read

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Far from bad practice  Python  and other languages   extended the for loop structure so part of it will only be executed if the loop doesn t break   for n in range 5       for m in range 3           if m  gt   n              print  stop                break         print m  end          else          print  finished      Output   stop  0 stop  0 1 stop  0 1 2 finished  0 1 2 finished      Equivalent code without break and that handy else   for n in range 5       aborted   False     for m in range 3           if not aborted              if m  gt   n                  print  stop                    aborted   True             else                              print m  end          if not aborted          print  finished

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I agree with others who recommend using break   The obvious consequential question is why would anyone recommend otherwise   Well    when you use break  you skip the rest of the code in the block  and the remaining iterations   Sometimes this causes bugs  for example    a resource acquired at the top of the block may be released at the bottom  this is true even for blocks inside for loops   but that release step may be accidentally skipped when a  premature  exit is caused by a break statement   in  modern  C     RAII  is used to handle this in a reliable and exception-safe way  basically  object destructors free resources reliably no matter how a scope is exited  someone may change the conditional test in the for statement without noticing that there are other delocalised exit conditions ndim s answer observes that some people may avoid breaks to maintain a relatively consistent loop run-time  but you were comparing break against use of a boolean early-exit control variable where that doesn t hold   Every now and then people observing such bugs realise they can be prevented mitigated by this  no breaks  rule    indeed  there s a whole related strategy for  safer  programming called  structured programming   where each function is supposed to have a single entry and exit point too  i e  no goto  no early return    It may eliminate some bugs  but it doubtless introduces others   Why do they do it      they have a development framework that encourages a particular style of programming   code  and they ve statistical evidence that this produces a net benefit in that limited framework  or they ve been influenced by programming guidelines or experience within such a framework  or they re just dictatorial idiots  or any of the above   historical inertia  relevant in that the justifications are more applicable to C than modern C

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It depends on the language  While you can possibly check a boolean variable here   for  int i   0  i  lt  100  amp  amp  stayInLoop  i              it is not possible to do it when itering over an array   for element in bigList        Anyway  break would make both codes more readable

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General rule  If following a rule requires you to do something more awkward and difficult to read then breaking the rule  then break the rule   In the case of looping until you find something  you run into the problem of distinguishing found versus not found when you get out  That is   for  int x 0 x lt fooCount   x      Foo foo getFooSomehow x     if  foo bar  42      break       So when we get here  did we find one  or did we fall out the bottom    So okay  you can set a flag  or initialize a  found  value to null  But   That s why in general I prefer to push my searches into functions   Foo findFoo int wantBar      for  int x 0 x lt fooCount   x          Foo foo getFooSomehow x       if  foo bar  wantBar        return foo           Not found   return null      This also helps to unclutter the code  In the main line   find  becomes a single statement  and when the conditions are complex  they re only written once

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Lots of answers here  but I haven t seen this mentioned yet   Most of the  dangers  associated with using break or continue in a for loop are negated if you write tidy  easily-readable loops  If the body of your loop spans several screen lengths and has multiple nested sub-blocks  yes  you could easily forget that some code won t be executed after the break  If  however  the loop is short and to the point  the purpose of the break statement should be obvious   If a loop is getting too big  use one or more well-named function calls within the loop instead  The only real reason to avoid doing so is for processing bottlenecks

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break is a completely acceptable statement to use  so is continue  btw   It s all about code readability -- as long as you don t have overcomplicated loops and such  it s fine    It s not like they were the same league as goto

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It s perfectly valid to use break - as others have pointed out  it s nowhere in the same league as goto    Although you might want to use the vFound variable when you want to check outside the loop whether the value was found in the array  Also from a maintainability point of view  having a common flag signalling the exit criteria might be useful

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In the embedded world  there is a lot of code out there that uses the following construct       while 1                  if  RCIF             gx             if  command received    command we are waiting on             break           else if   num attempts  gt  MAX ATTEMPTS      TickGet   - BaseTick  gt  MAX TIMEOUT              return ERROR           num attempts              if  call some bool returning function          return TRUE      else       return FALSE    This is a very generic example  lots of things are happening behind the curtain  interrupts in particular   Don t use this as boilerplate code  I m just trying to illustrate an example   My personal opinion is that there is nothing wrong with writing a loop in this manner as long as appropriate care is taken to prevent remaining in the loop indefinitely

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No  break is the correct solution   Adding a boolean variable makes the code harder to read and adds a potential source of errors

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I did some analysis on the codebase I m currently working on  40 000 lines of JavaScript    I found only 22 break statements  of those    19 were used inside switch statements  we only have 3 switch statements in total    2 were used inside for loops - a code that I immediately classified as to be refactored into separate functions and replaced with return statement  As for the final break inside while loop    I ran git blame to see who wrote this crap    So according to my statistics  If break is used outside of switch  it is a code smell   I also searched for continue statements  Found none

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In your example you do not know the number of iterations for the for loop  Why not use while loop instead  which allows the number of iterations to be indeterminate at the beginning    It is hence not necessary to use break statemement in general  as the loop can be better stated as a while loop

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You can find all sorts of professional code with  break  statements in them  It perfectly make sense to use this whenever necessary  In your case this option is better than creating a separate variable just for the purpose of coming out of the loop

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Using break as well as continue in a for loop is perfectly fine   It simplifies the code and improves its readability

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Ofcourse  break  is the solution to stop the for loop or foreach loop  I used it in php in foreach and for loop and found working

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I don t see any reason why it would be a bad practice PROVIDED that you want to complete STOP processing at that point

[for-loop] Is it a bad practice to use break in a for loop?

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