Why is it not possible to break out of an if statement? [closed]

Question

in C or C++:

why can't we use break; to break an if statement?

if( color == red ) {
  ...
  if( car == hyundai ) break;
  ...
}

But, why is it exactly, that it does no work ?

Answer 1

The simplest reason is "its not how the language was designed." You just can't.

The reason why you can't is speculation (I haven't been able to find any writings about it being a good idea), though thinking about it, there are likely good reasons for this that can be identified.

There is no good reason for a structure that is if(foo) { doStuff(); if(bar) break; doOtherStuff(); } This control structure can be done in a mulitude of other ways that don't need a break: if(foo) { doStuff(); if(!bar) { doOtherStuff(); } }

break is often used as part of an if block: while(true) { ... if(foo) { break; } ... } If break was to be breaking out of the if context rather than the while context, then labels would be required nearly everywhere: LOOP: while(true) { ... if(foo) { break LOOP; } ... }. Some people like using labels everywhere (and some people deplore the use of a labeled break), but it certainly adds to the clutter in the code.

At this point (having to label loops) it doesn't look too bad, it would mean that any breakable structure would need to be labeled if there is another breakable structure nested within it. This rapidly becomes a potential nightmare to code to.

This boils down to "there is no good use case for a break to break out of an if scope and if such design choice was made, it would have made code much uglier and harder to read (labels are global - every loop would need to be labeled in this global name space).

Related StackOverflow reading:

• http://stackoverflow.com/questions/4851657/call-break-in-nested-if-statements
• http://stackoverflow.com/questions/7468836/any-way-to-break-if-statement-in-php
• http://stackoverflow.com/questions/8523538/how-do-i-break-out-of-an-if-statement

Answer 2

If you want to break out of the if block while still inside it, use a goto statement. Alternatively, rewrite your code so that you don't need to break out of it in the first place, which is usually a better idea.

Also, this question is better asked on Stack Overflow. This site is for conceptual questions, not implementation questions.

Answer 3

An if statement is a conditional branching mechanism to alter conditional flow of logic in a thread or process. There is no breaking out of it because it is not a loop.