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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 78 |
1 files changed, 78 insertions, 0 deletions
@@ -10056,6 +10056,84 @@ variable syntax. Within \*(TL, regular expressions are written with a leading .codn # . +.NP* Package Prefixes + +If a symbol name contains a colon, the +.I lident +characters, if any, before that colon constitute the package prefix. +It is erroneous to read a symbol whose package doesn't exist. +If the package exist, the symbol is interned in that package. + +If the package name is an empty identifier, the package is understood to be the +.code keyword +package and the symbol is a self-evaluating keyword symbol. + +For example +.code foo:bar +is the +.code bar +symbol in the +.code foo +package. + +The syntax +.code :test +denotes the symbol +.code test +in the +.code keyword +package, the same as +.codn keyword:test . + +The syntax +.code @foo:bar +denotes the meta prefix +.code @ +being applied to the +.code foo:bar +symbol, not to a symbol in the +.code @foo +package. + +The syntax +.code #:bar +denotes an uninterned symbol named +.codn bar , +described in the next section. + +.TP* "Dialect note:" +In ANSI Common Lisp, the +.code foo:bar +syntax does not create the symbol +.code bar +in the +.code foo +package; the symbol must exist or else the syntax is erroneous. +In \*(TL, only the package has to exist; the symbol will be interned +in that package. + +.NP* Uninterned Symbols + +Uninterned symbols are written with the +.code #: +prefix, followed by zero or more +.I lident +characters. +When an uninterned symbol is read, a new, unique symbol is constructed, +with the specified name. Even if two uninterned symbols have the same name, +they are different objects. The +.code make-sym +and +.code gensym +functions produce uninterned symbols. + +"Uninterned" means "not entered into a package". Interning refers to a +process which combines package lookup with symbol creation, which ensures +that multiple occurrences of a symbol name in written syntax are all converted +to the same object: the first occurrence creates the symbol and associates it +with its name in a package. Subsequent occurrences do not create a new symbol, +but retrieve the existing one. + .NP* Consing Dot Unlike other major Lisp dialects, \*(TL allows a consing dot with no forms |