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Diffstat (limited to 'doc/lispref/eval.texi')
| -rw-r--r-- | doc/lispref/eval.texi | 50 |
1 files changed, 31 insertions, 19 deletions
diff --git a/doc/lispref/eval.texi b/doc/lispref/eval.texi index a65b2346300..b42020f43af 100644 --- a/doc/lispref/eval.texi +++ b/doc/lispref/eval.texi @@ -252,11 +252,8 @@ the original symbol. If the contents are another symbol, this process, called @dfn{symbol function indirection}, is repeated until it obtains a non-symbol. @xref{Function Names}, for more information about symbol function indirection. - - One possible consequence of this process is an infinite loop, in the -event that a symbol's function cell refers to the same symbol. -Otherwise, we eventually obtain a non-symbol, which ought to be a -function or other suitable object. +We eventually obtain a non-symbol, which ought to be a function or +other suitable object. @kindex invalid-function More precisely, we should now have a Lisp function (a lambda @@ -332,19 +329,17 @@ or just The built-in function @code{indirect-function} provides an easy way to perform symbol function indirection explicitly. -@defun indirect-function function &optional noerror +@defun indirect-function function @anchor{Definition of indirect-function} This function returns the meaning of @var{function} as a function. If @var{function} is a symbol, then it finds @var{function}'s function definition and starts over with that value. If @var{function} is not a symbol, then it returns @var{function} itself. -This function returns @code{nil} if the final symbol is unbound. It -signals a @code{cyclic-function-indirection} error if there is a loop -in the chain of symbols. +This function returns @code{nil} if the final symbol is unbound. -The optional argument @var{noerror} is obsolete, kept for backward -compatibility, and has no effect. +There is also a second, optional argument that is obsolete and has no +effect. Here is how you could define @code{indirect-function} in Lisp: @@ -745,13 +740,17 @@ type of the @var{form} object determines how it is evaluated. @xref{Forms}. The argument @var{lexical} specifies the scoping rule for local -variables (@pxref{Variable Scoping}). If it is omitted or @code{nil}, -that means to evaluate @var{form} using the default dynamic scoping -rule. If it is @code{t}, that means to use the lexical scoping rule. -The value of @var{lexical} can also be a non-empty alist specifying a +variables (@pxref{Variable Scoping}). If it is @code{t}, that means +to evaluate @var{form} using lexical scoping; this is the recommended +value. If it is omitted or @code{nil}, that means to use the old +dynamic-only variable scoping rule. + +The value of @var{lexical} can also be a non-empty list specifying a particular @dfn{lexical environment} for lexical bindings; however, this feature is only useful for specialized purposes, such as in Emacs -Lisp debuggers. @xref{Lexical Binding}. +Lisp debuggers. Each member of the list is either a cons cell which +represents a lexical symbol-value pair, or a symbol representing a +(special) variable that would use dynamic scoping if bound. Since @code{eval} is a function, the argument expression that appears in a call to @code{eval} is evaluated twice: once as preparation before @@ -845,11 +844,24 @@ function body forms, as well as explicit calls in Lisp code. The default value of this variable is 1600. If you set it to a value less than 100, Lisp will reset it to 100 if the given value is -reached. Entry to the Lisp debugger increases the value, if there is -little room left, to make sure the debugger itself has room to -execute. +reached. @end defopt +@defopt lisp-eval-depth-reserve +In order to be able to debug infinite recursion errors, when invoking the +Lisp debugger, Emacs increases temporarily the value of +@code{max-lisp-eval-depth}, if there is little room left, to make sure +the debugger itself has room to execute. The same happens when +running the handler of a @code{handler-bind}. @xref{Handling Errors}. + +The variable @code{lisp-eval-depth-reserve} bounds the extra depth +that Emacs can add to @code{max-lisp-eval-depth} for those +exceptional circumstances. + +The default value of this variable is 200. +@end defopt + + @defvar values The value of this variable is a list of the values returned by all the expressions that were read, evaluated, and printed from buffers |