I get the impression that the original quote from the book is using "name space" as it's used in other languages outside of CL, except that the book is from 1992 so not sure if that usage was widespread yet - maybe in C++? But it's almost like they wanted to say "a package is analogous to a name space as it's used in [algol-derivative]." Definite potential for confusion there, since "namespace" has a very specific meaning in CL and in general helps explain the difference between Lisp-1 and Lisp-2 (Lisp-n) varieties.
The quote is in the Preface, which is outside of the book itself. The same paragraph acknowledges that "packages can be very confusing for Lispers who have not learned about them in an organized way" and that the author has "seen experienced, Ph.D.-level Lispers hack away, adding qualifications to symbol names in their code, with no understanding of the organized structure of the package system." Furthermore, he adds that "[t]he reasons that packages are even more confusing in Lisp than in other, compiler-oriented languages, such
as Ada, is that in Lisp one may introduce symbols on-line, and one typically stays in one Lisp environment for hours, losing track of what symbols have been introduced. A symbol naming conflict may be introduced in the course of debugging that will not occur when the fully developed files are loaded into a fresh environment in the proper order."
After that, nobody in their right mind should be hanging on to any preconceived notion that they might have spun out of the earlier phrase "multiple name spaces of symbols", and should be reading the actual book.
> nobody in their right mind should be hanging on to any preconceived notion that they might have spun out of the earlier phrase "multiple name spaces of symbols"
Except that "namespace" is a term of art which is actually defined in the Common Lisp standard, and so it is not unreasonable to suppose that this is the intended meaning in a book on Common Lisp.
namespace n. 1. bindings whose denotations are restricted to a particular kind. ``The bindings of names to tags is the tag namespace.'' 2. any mapping whose domain is a set of names. ``A package defines a namespace.''
So if "the bindings of names to tags is the tag namespace", that means that a set of bindings of names to symbols is a symbol namespace!
According to the Common Lisp Glossary, the values of the dictionary define what the namespace is of. Of course the keys are always names; that's what makes it a namespace.
Also, look: "a package defines a namespace" (and it must be one of symbols).
You're not catching crafty old Shapiro red-handed in anything here.
> So if "the bindings of names to tags is the tag namespace", that means that a set of bindings of names to symbols is a symbol namespace!
No, that does not follow. Even if one were to admit the parallel construct here, the result would be "the symbol namespace" which is clearly nonsense.
Neither "tag namespace" nor "symbol namespace" is a term of art, so here we are in the domain of natural language, and natural language is irregular and ambiguous. In natural language usage, a "namespace for symbols" is one where symbols are the domain, not the range. In particular, the most common usage is to distinguish between Lisp-1 and Lisp-2, where the former has a single namespace for symbols and the latter has at least two, one for values and one for functions.
