diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 56 |
1 files changed, 52 insertions, 4 deletions
@@ -36785,11 +36785,45 @@ parameter. Using these functions, a macro can enquire whether a given .meta form is a symbol which has a variable binding or a function binding -in the lexical environment. +in the local lexical environment. This information is known during macro expansion. The macro expander recognizes lexical function and variable bindings, because these bindings can shadow macros. +Special variables are not lexical. The function +.code lexical-var-p +returns +.code nil +if +.meta form +satisfies +.code special-var-p +function, indicating that it is the name of a special variable. + +The +.code lexical-var-p +function also returns +.code nil +for global lexical variables. If +.meta form +is a symbol for which only a global lexical variable binding is apparent, +.code lexical-var-p +returns +.codn nil . +Testing for the existence for a global variable can be done using +.codn boundp ; +if a symbol is +.code boundp +but not +.codn special-var-p , +then it is a global lexical variable. + +Similarly, +.code lexical-fun-p +returns +.code nil +for global functions. + .TP* Example: .verb @@ -36806,14 +36840,20 @@ bindings can shadow macros. (t :not-lex-fun-var))) ;; - ;; This returns: - ;; - ;; (:lexical-var :not-lex-fun-var :lexical-fun) + ;; Use classify macro above to report classification + ;; of the x, y and f symbols in the given scope ;; (let ((x 1) (y 2)) (symacrolet ((y x)) (flet ((f () (+ 2 2))) (list (classify x) (classify y) (classify f))))) + --> (:lexical-var :not-lex-fun-var :lexical-fun) + + ;; Locally bound specials are not lexical + + (let ((*stdout* *stdnull*)) + (classify *stdout*)) + --> :not-lex-fun-var .brev .TP* Note: @@ -79273,6 +79313,14 @@ A compatibility value of 248 or lower restores the above old behaviors of .code @ and .codn hash-revget . +.IP 257 +Until \*(TX 257, the function +.code lexical-var-p +returned +.code t +for not only lexical variables, but also for locally bound special variables, +which are not lexical. The behavior is restored if 257 or older compatibility +is selected. .IP 244 Until \*(TX 244, the .code env-hash |