Mark H Weaver <m...@netris.org> writes: About undefined?: That was a typo. I mentioned that in a later message.
> It's nonsensical to ask whether a given object is "unspecified". When > the Scheme standards say that the result of a computation is an > unspecified value, that means that *any* Scheme object could be > returned. > > In Guile, for historical reasons, we usually return a particular object > SCM_UNSPECIFIED (a.k.a. *unspecified*) in cases where the specification > says that the result is unspecified. However, we make no promises that > this will remain the case in future versions of Guile. > > The number of legitimate uses for 'unspecified?' is extremely small. In > fact, I can think of only one: when a REPL prints the result of a user's > computation, it is nice to avoid printing "*unspecified*" and instead > print nothing in that case. > > In almost every other case, use of 'unspecified?' implies an assumption > that it's possible to detect when a value is an "unspecified" value, > when in fact that is fundamentally impossible. > > What do you think? I agree. I didn't put very much thought into the matter before I sent the patch. I needed unspecified? for a patch to GNU Guix. I found the info documentation missing for unspecified? and thought I'll write it. Later, it turned out unspecified? was not necessary for the Guix patch after all. But, I had already documented unspecified?. So, I sent it here. Anyways, I'll close this bug report.
