ANSI Common Lisp 2 Syntax 2.3 Interpretation of Tokens
2.3.5 Valid Patterns for Tokens
The valid patterns for tokens are summarized in the next figure.
Note that nnnnn has number syntax,
neither xxxxx nor ppppp has number syntax,
and aaaaa has any syntax.
A summary of rules concerning package markers follows.
In each case, examples are offered to illustrate the case;
for presentational simplicity, the examples assume that
the readtable case of the current readtable is :upcase.
If there is a single package marker, and it occurs at the beginning of the
token, then the token is interpreted as a symbol in the keyword package.
It also sets the symbol-value of the newly-created symbol to that
same symbol so that the symbol will self-evaluate.
:bar, when read, interns BAR as an external symbol in the keyword package.
If there is a single package marker not at the beginning or end of the
token, then it divides the token into two parts. The first part
specifies a package;
the second part is the name of an external symbol
available in that package.
foo:bar, when read, looks up BAR among the external symbols of
the package named FOO.
If there are two adjacent package markers not at the beginning or end of the
token, then they divide the token into two parts. The first part
specifies a package;
the second part is the name of a symbol within
that package (possibly an internal symbol).
foo::bar, when read, interns BAR in the package named FOO.
If the token contains no package markers,
and does not have potential number syntax,
then the entire token is the name of the symbol.
The symbol is looked up in the current package.
bar, when read, interns BAR in the current package.
The consequences are unspecified if any other pattern of package markers
in a token is used.
All other uses of package markers within names of symbols
are not defined by this standard
but are reserved for implementation-dependent use.
assuming the readtable case of the current readtable is :upcase,
editor:buffer refers to the external symbol
named BUFFER present in the package named editor,
regardless of whether there is a symbol named BUFFER in
the current package. If there is no package named
editor, or if no symbol named BUFFER
is present in editor, or if BUFFER is not exported by
editor, the reader signals
a correctable error.
If editor::buffer is seen, the effect is exactly the same as
reading buffer with the editor package being the current package.