Do you use curly braces for additional scoping? [closed]

Answer 1

It can be a boon to code generators. Suppose you have an Embedded SQL (ESQL) compiler; it might want to convert an SQL statement into a block of code that needs local variables. By using a block, it can reuse fixed variable names over and over, rather than having to create all the variables with separate names. Granted, that's not too hard, but it is harder than necessary.

Answer 2

As others have said, this is fairly common in C++ due to the all-powerful RAII (resource acquisition is initialization) idiom/pattern.

For Java programmers (and maybe C#, I don't know) this will be a foreign concept because heap-based objects and GC kills RAII. IMHO, being able to put objects on the stack is the greatest single advantage of C++ over Java and makes well-written C++ code MUCH cleaner than well-written Java code.

Answer 3

C++:

Sometimes you need to introduce an extra brace level of scope to reuse variable names when it makes sense to do so:

switch (x) {
    case 0:
        int i = 0;
        foo(i);
        break;
    case 1:
        int i = 1;
        bar(i);
        break;
}

The code above doesn't compile. You need to make it:

switch (x) {
    case 0:
        {
            int i = 0;
            foo(i);
        }
        break;
    case 1:
        {
            int i = 1;
            bar(i);
        }
        break;
}

Answer 4

The company I'm working at has a static analysis policy to keep local variable declarations near the beginning of a function. Many times, the usage is many lines after the first line of a function so I cannot see the declaration and the first reference at the same time on the screen. What I do to 'circumvent' the policy is to keep the declaration near the reference, but provide additional scope by using curly braces. It increases indentation though, and some may argue that it makes the code uglier.

Answer 5

I would not use curly braces for that purpose for a couple reasons.

1. If your particular function is big enough that you need to do various scoping tricks, perhaps break the function into smaller sub-functions.

2. Introducing braces for scoping to reuse variable names is only going to lead to confusion and trouble in code.

Just my 2 cents, but I have seen a lot of these types of things in other best practice materials.

Answer 6

It has its place, but I don't think that doing it so that $foo can be one variable here and a different variable there, within the same function or other (logical, rather than lexical) scope is a good idea. Even though the compiler may understand that perfectly, it seems too likely to make life difficult for humans trying to read the code.