Comments on: The Open-Closure-Close Idiom in D

By: Alexander Panek

Alexander Panek — Sat, 16 Feb 2008 10:56:22 +0000

On the other hand, it’s easier to get an ol’ dog to sit, when you provide a warm, cozy pillow under his bottom. Think of scope as your warm, cozy pillow.

By: Hans-Eric

Hans-Eric — Fri, 15 Feb 2008 11:40:04 +0000

I’m bound to agree. That is a nicer looking implementation.

By: Hans-Eric

Hans-Eric — Fri, 15 Feb 2008 11:37:52 +0000

Indeed, scope is a great feature. For some reason I seem to be reluctant to use it. I’m sure that’s just because, as we say in Sweden, “it’s difficult to learn old dogs to sit.”

By: Alexander Panek

Alexander Panek — Thu, 14 Feb 2008 10:38:32 +0000

I think this looks way neater without try {} finally {}, but rather the oh-so-bad “new” syntax scope(exit):

Stream open(char[] fn, FileMode fm = FileMode.In, void delegate(Stream) closure = null) { Stream f = new File(fn, fm);


	if (closure !is null) {

		scope(exit) f.close;

		return closure(f);

	} else return f;

}

// Example usage r”C:\log.txt”.open(FileMode.Out, (Stream f) { OutputStream os = f; os.writefln(”Log this”); });

By: David Wilson

David Wilson — Thu, 14 Feb 2008 10:27:01 +0000

The D language has a “scope” keyword, as mentioned in the documentation. Basicall instead of all that jazz from the article, simply:

void doSomething()
{
scope f = new File(”/log.txt’, …);

/* do work */
}

void main()
{
doSomething();
/* f is guaranteed by specification not to exist by
this point, regardless of exceptions. */
}