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    <p>Let's attempt to also modify <code>i</code> when we increment <code>j</code>:</p> <pre><code>int j = 0; for (int i = 0 ; i &lt; 100 ; ++i) if (i % 2 == 0) j++; i++; </code></pre> <p>Oh no! Coming from Python, this looks ok, but in fact it isn't, as it's equivalent to:</p> <pre><code>int j = 0; for (int i = 0 ; i &lt; 100 ; ++i) if (i % 2 == 0) j++; i++; </code></pre> <p>Of course, this is a silly mistake, but one that even an experienced programmer could make.</p> <p><strong>Another very good reason</strong> is pointed out in <a href="https://stackoverflow.com/a/12193223/673730">ta.speot.is's answer</a>.</p> <p><strong>A third</strong> one I can think of is nested <code>if</code>'s:</p> <pre><code>if (cond1) if (cond2) doSomething(); </code></pre> <p>Now, assume you now want to <code>doSomethingElse()</code> when <code>cond1</code> is not met (new feature). So:</p> <pre><code>if (cond1) if (cond2) doSomething(); else doSomethingElse(); </code></pre> <p>which is obviously wrong, since the <code>else</code> associates with the inner <code>if</code>.</p> <hr> <p>Edit: Since this is getting some attention, I'll clarify my view. The question I was answering is:</p> <blockquote> <p>What's the benefit of using the 1st version?</p> </blockquote> <p>Which I have described. There are some benefits. But, IMO, "always" rules don't always apply. So I don't wholly support</p> <blockquote> <p>Always use a { } block - even for a single line // not OK, why ???</p> </blockquote> <p>I'm not saying <em>always</em> use a <code>{}</code> block. If it's a simple enough condition &amp; behavior, don't. If you suspect someone might come in later &amp; change your code to add functionality, do.</p>
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    1. POWhat's the purpose of using braces (i.e. {}) for a single-line if or loop?
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    1. USLuchian Grigore
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    1. POWhat's the purpose of using braces (i.e. {}) for a single-line if or loop?
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    1. CONice, but just two points. 1) Even worse is having j++;i++; on same line thinking it is okay, its not. 2) A good IDE should tell you that i is unidentified since it is out of scope.
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      1. USScience_Fiction
    2. CO@Science_Fiction: True, but if you add `i++` *before* `j++`, then both variables will still be in scope when they're used.
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      1. USMike Seymour
    3. COThis sounds very reasonable, but neglects the fact that the editor does the indentation, not you, and it will indent the `i++;` in a way that shows immediately that it is not part of the loop. (In the past, this might have been a reasonable argument, and I've seen such problems. About 20 years ago. Not since.)
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      1. USJames Kanze
 

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