Re: Return of nested function

[Johannes Bauer]

Nick Keighley schrieb:

>- I use GCC (and its extension for the nested functions)

ah. As you note this is a gcc extension. You need to ask on
a gcc group for the exact semantics of their nested functions

Why is there actually a *need* for nested functions? If functionality of
subfunctions which are only locally visible is desired, why not put the
nesting function parent and its nested children all in one module,
declare the children static - voila. Std-C.

Regards,
Johannes

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[Chris Dollin]

Johannes Bauer wrote:

Nick Keighley schrieb:

>>- I use GCC (and its extension for the nested functions)

ah. As you note this is a gcc extension. You need to ask on
a gcc group for the exact semantics of their nested functions

Why is there actually a *need* for nested functions? If functionality of
subfunctions which are only locally visible is desired, why not put the
nesting function parent and its nested children all in one module,
declare the children static - voila. Std-C.

It's possible (even likely) that the GCC semantics is more powerful
than this would allow. For example, it might implement Pascal-style
nesting, where functions can refer to the locals of the functions
they are nested in while those functions are still executing.

/Clearly/ you can fabricate code to get round this, unless (as
you likely will) you have to pass your function-plus-fabrications
through a function-pointer-sized-and-typed slot. Oops.

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[Richard Tobin]

In article <30************@joeserver.homelan.net>,
Johannes Bauer <df***********@gmx.dewrote:

>Why is there actually a *need* for nested functions? If functionality of
subfunctions which are only locally visible is desired, why not put the
nesting function parent and its nested children all in one module,
declare the children static - voila. Std-C.

Is there actually a *need* for local variables? If functionality of
variables which are only locally visible is desired, why not put the
function in a file by itself and declare the variables static at file
scope - voila.

The point, of course, is that nested functions can do more than
control the visibility of the function name. They let you create
closures - instances of functions that are "closed" over the bindings
of variables in enclosing scopes.

[Yes, you could have an implementation of nested functions that didn't
provide this, just as you could have an implementation of local
variables that didn't make recursive calls work. Then they really
wouldn't be much use.]

-- Richard
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