Question

We can declare functions inside functions (I wanted a local variable, but it parses as a function declaration):

struct bvalue;
struct bdict {
    bdict(bvalue);
}
struct bvalue {
    explict operator bdict() const;
}
struct metainfo {
    metainfo(bdict);
}
void foo(bvalue v) {
    metainfo mi(bdict(v)); // parses as function declaration
    metainfo mi = bdict(v); // workaround
                            // (this workaround doesn't work in the presence of explicit ctors)
}

Are the sole reasons “because it makes the parser simpler” and “because the standard says so”, or is there an obscure use for this?

Answer 1

This is really a C question, because this behaviour was inherited directly from C (although it gets much more press in C++ because of the most vexing parse).

I suspect the answer (in the context of C, at least) is that this allows you to scope the existence of your function declarations to precisely where they’re needed. Maybe that was useful in the early days of C. I doubt anyone does that any more, but for the sake of backward compatibility it can’t be removed from the language.