What's the purpose of using braces (i.e. {}) for a single-line if or loop?

Question

I\'m reading some lecture notes of my C++ lecturer and he wrote the following:

1. Use Indentation // OK
2. Never rely on operator preced

Answer 1

I like Luchian's accepted answer, in fact I learned the hard way that he is right, so I do always use braces, even for single-line blocks. However, personally I make an exception when writing a filter, as you are in your example. This:

int j = 0;
for (int i = 0 ; i < 100 ; ++i)
{
    if (i % 2 == 0)
    {
        j++;
    }
}

looks cluttered to me. It separates the for loop and the if statement into separate actions, when really your intent is a single action: to count all of the integers divisible by 2. In a more expressive language, this could be written something like:

j = [1..100].filter(_%2 == 0).Count

In languages which lack closures, the filter cannot be expressed in a single statement, but must be a for loop followed by an if statement. However, it is still one action in the mind of the programmer, and I believe that should be reflected in the code, like so:

int j = 0;
for (int i = 0 ; i < 100 ; ++i)
  if (i % 2 == 0)
{
    j++;
}