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 precedence - Always use parentheses // OK > 3. Always use a { } block - even for a single line // **not OK**, why ??? > 4. Const object on left side of comparison // OK > 5. Use unsigned for variables that are >= 0 // nice trick > 6. Set Pointer to NULL after deletion - Double delete protection // not bad The 3rd technique is not clear to me: what would I gain by placing one line in a `{ ... }`? For example, take this weird code:  int j = 0;  for (int i = 0 ; i < 100 ; ++i)  {   if (i % 2 == 0)   {    j++;   }  } and replace it with:  int j = 0;  for (int i = 0 ; i < 100 ; ++i)   if (i % 2 == 0)    j++; What's the benefit of using the 1st version?

Answer 1

Well, it's mainly an issue of code clarity/consistency and simplifying code modification.

I for one, wish that the single-statement code block {} exception was not permitted in the language ... it doesn't buy us much - in fact, I think it generates more confusion than benefit, and led to this rather ambiguous "best practice" that you're asking about now.

I've wondered if Dennis Richie felt the same way in retrospect ;-)

Anyway, a rapidly evolving program often expands on logical and repetitive code blocks, perhaps increasing the number of statements in the block from 1 to >1.

It's simply more straightforward and less prone to error to go FROM:

if( condition ) {

statement;

}

while( condition ) {

statement;

}

TO

if( condition ) {

statement1;

statement2;

}

while( condition ) {

statement1;

statement2;

}

THAN FROM

if( condition )

statement;

while( condition )

statement;

TO

if( condition ) {

statement1;

statement2;

}

while( condition ) {

statement1;

statement2;

}

A developer might inadvertently re-code to something like this:

if( condition )

statement1;

statement2; // intended to be part of if block - introducing a subtle bug - statement2 will execute unconditionally ....

Might the chances of making this mistake be lower if the { } were always used to implement a code block?

I think so!