Using lambdas to do nested functions

Question

What's everybody's opinion on using lambdas to do nested functions in C++? For example, instead of this:

static void prepare_eggs()
{
   ...
}

static void prepare_ham()
{
   ...
}

static void prepare_cheese()
{
   ...
}

static fry_ingredients()
{
   ...
}

void make_omlette()
{
    prepare_eggs();
    prepare_ham();
    prepare_cheese();
    fry_ingredients();
}

You do this:

void make_omlette()
{
    auto prepare_eggs = [&]()
    {
       ...
    };

    auto prepare_ham = [&]()
    {
       ...
    };

    auto prepare_cheese = [&]()
    {
       ...
    };

    auto fry_ingredients = [&]()
    {
       ...
    };


    prepare_eggs();
    prepare_ham();
    prepare_cheese();
    fry_ingredients();
}

Having come from the generation that learned how to code by using Pascal, nested functions make perfect sense to me. However, this usage seemed to confuse some of the less experienced developers in my group at work during a code review where I made use of lambdas in this way.

Answer 1

I don't see anything wrong with nested functions per se. I use lambdas for nested functions, but only if it meets some conditions:

• It is called in more than once place. (otherwise just write the code directly if it's not too long)
• It is really an internal function, so that that calling it in any other context would not make sense.
• It's short enough (maybe 10 lines max).

So in your example I would not use lambdas for reason number one.

Conceptually nested functions can be useful for the same reason why private methods in classes are useful. They enforce encapsulation and they make it easier to see the structure of the program. If a function is an implementation detail to some other function then why not make it explicitly so?

The biggest problem I see is with readability; it's more difficult to read code that has a lot of nesting and indenting. Also, people are not very comfortable with lambdas yet so resistance is expected.