view man/lispref/errors.texi @ 5366:f00192e1cd49

Examining the result of #'length: `eql', not `=', it's better style & cheaper 2011-03-08 Aidan Kehoe <kehoea@parhasard.net> * buff-menu.el (list-buffers-noselect): * byte-optimize.el (byte-optimize-identity): * byte-optimize.el (byte-optimize-if): * byte-optimize.el (byte-optimize-nth): * byte-optimize.el (byte-optimize-nthcdr): * bytecomp.el (byte-compile-warn-wrong-args): * bytecomp.el (byte-compile-two-args-19->20): * bytecomp.el (byte-compile-list): * bytecomp.el (byte-compile-beginning-of-line): * bytecomp.el (byte-compile-set): * bytecomp.el (byte-compile-set-default): * bytecomp.el (byte-compile-values): * bytecomp.el (byte-compile-values-list): * bytecomp.el (byte-compile-integerp): * bytecomp.el (byte-compile-multiple-value-list-internal): * bytecomp.el (byte-compile-throw): * cl-macs.el (cl-do-arglist): * cl-macs.el (cl-parse-loop-clause): * cl-macs.el (multiple-value-bind): * cl-macs.el (multiple-value-setq): * cl-macs.el (get-setf-method): * cmdloop.el (command-error): * cmdloop.el (y-or-n-p-minibuf): * cmdloop.el (yes-or-no-p-minibuf): * coding.el (unencodable-char-position): * cus-edit.el (custom-face-prompt): * cus-edit.el (custom-buffer-create-internal): * cus-edit.el (widget-face-action): * cus-edit.el (custom-group-value-create): * descr-text.el (describe-char-unicode-data): * dialog-gtk.el (popup-builtin-question-dialog): * dragdrop.el (experimental-dragdrop-drop-log-function): * dragdrop.el (experimental-dragdrop-drop-mime-default): * easymenu.el (easy-menu-add): * easymenu.el (easy-menu-remove): * faces.el (read-face-name): * faces.el (set-face-stipple): * files.el (file-name-non-special): * font.el (font-combine-fonts): * font.el (font-set-face-font): * font.el (font-parse-rgb-components): * font.el (font-rgb-color-p): * font.el (font-color-rgb-components): * gnuserv.el (gnuserv-edit-files): * help.el (key-or-menu-binding): * help.el (function-documentation-1): * help.el (function-documentation): * info.el (info): * isearch-mode.el (isearch-exit): * isearch-mode.el (isearch-edit-string): * isearch-mode.el (isearch-*-char): * isearch-mode.el (isearch-complete1): * ldap.el (ldap-encode-country-string): * ldap.el (ldap-decode-string): * minibuf.el (read-file-name-internal-1): * minibuf.el (read-non-nil-coding-system): * minibuf.el (get-user-response): * mouse.el (drag-window-divider): * mule/ccl.el: * mule/ccl.el (ccl-compile-if): * mule/ccl.el (ccl-compile-break): * mule/ccl.el (ccl-compile-repeat): * mule/ccl.el (ccl-compile-write-repeat): * mule/ccl.el (ccl-compile-call): * mule/ccl.el (ccl-compile-end): * mule/ccl.el (ccl-compile-read-multibyte-character): * mule/ccl.el (ccl-compile-write-multibyte-character): * mule/ccl.el (ccl-compile-translate-character): * mule/ccl.el (ccl-compile-mule-to-unicode): * mule/ccl.el (ccl-compile-unicode-to-mule): * mule/ccl.el (ccl-compile-lookup-integer): * mule/ccl.el (ccl-compile-lookup-character): * mule/ccl.el (ccl-compile-map-multiple): * mule/ccl.el (ccl-compile-map-single): * mule/devan-util.el (devanagari-compose-to-one-glyph): * mule/devan-util.el (devanagari-composition-component): * mule/mule-cmds.el (finish-set-language-environment): * mule/viet-util.el: * mule/viet-util.el (viet-encode-viscii-char): * multicast.el (open-multicast-group): * newcomment.el (comment-quote-nested): * newcomment.el (comment-region): * newcomment.el (comment-dwim): * regexp-opt.el (regexp-opt-group): * replace.el (map-query-replace-regexp): * specifier.el (derive-device-type-from-tag-set): * subr.el (skip-chars-quote): * test-harness.el (test-harness-from-buffer): * test-harness.el (batch-test-emacs): * wid-edit.el (widget-choice-action): * wid-edit.el (widget-symbol-prompt-internal): * wid-edit.el (widget-color-action): * window-xemacs.el (push-window-configuration): * window-xemacs.el (pop-window-configuration): * window.el (quit-window): * x-compose.el (electric-diacritic): It's better style, and cheaper (often one assembler instruction vs. a C funcall in the byte code), to use `eql' instead of `=' when it's clear what numerical type a given result will be. Change much of our code to do this, with the help of a byte-compiler change (not comitted) that looked for calls to #'length (which always returns an integer) in its args.
author Aidan Kehoe <kehoea@parhasard.net>
date Tue, 08 Mar 2011 23:41:52 +0000
parents 576fb035e263
children
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@c -*-texinfo-*-
@c This is part of the XEmacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
@c See the file lispref.texi for copying conditions.
@setfilename ../../info/errors.info
@node Standard Errors, Standard Buffer-Local Variables, Building XEmacs and Object Allocation, Top
@appendix Standard Errors

  Here is the complete list of the error symbols in standard Emacs,
grouped by concept.  The list includes each symbol's message (on the
@code{error-message} property of the symbol) and a cross reference to a
description of how the error can occur.

  Each error symbol has an @code{error-conditions} property that is a
list of symbols.  Normally this list includes the error symbol itself
and the symbol @code{error}.  Occasionally it includes additional
symbols, which are intermediate classifications, narrower than
@code{error} but broader than a single error symbol.  For example, all
the errors in accessing files have the condition @code{file-error}.

  As a special exception, the error symbol @code{quit} does not have the
condition @code{error}, because quitting is not considered an error.

  @xref{Errors}, for an explanation of how errors are generated and
handled.

@table @code
@item @var{symbol}
@var{string}; @var{reference}.

@item error
@code{"error"}@*
@xref{Errors}.

@item quit
@code{"Quit"}@*
@xref{Quitting}.

@item args-out-of-range
@code{"Args out of range"}@*
@xref{Sequences Arrays Vectors}.

@item arith-error
@code{"Arithmetic error"}@*
See @code{/} and @code{%} in @ref{Numbers}.

@item beginning-of-buffer
@code{"Beginning of buffer"}@*
@xref{Motion}.

@item buffer-read-only
@code{"Buffer is read-only"}@*
@xref{Read Only Buffers}.

@item cyclic-function-indirection
@code{"Symbol's chain of function indirections contains a loop"}@*
@xref{Function Indirection}.

@c XEmacs feature
@item domain-error
@code{"Arithmetic domain error"}@*

@item end-of-buffer
@code{"End of buffer"}@*
@xref{Motion}.

@item end-of-file
@code{"End of file during parsing"}@*
This is not a @code{file-error}.@*
@xref{Input Functions}.

@item file-error
This error and its subcategories do not have error-strings, because the
error message is constructed from the data items alone when the error
condition @code{file-error} is present.@*
@xref{Files}.

@item file-locked
This is a @code{file-error}.@*
@xref{File Locks}.

@item file-already-exists
This is a @code{file-error}.@*
@xref{Writing to Files}.

@item file-supersession
This is a @code{file-error}.@*
@xref{Modification Time}.

@item invalid-byte-code
@code{"Invalid byte code"}@*
@xref{Byte Compilation}.

@item invalid-function
@code{"Invalid function"}@*
@xref{Classifying Lists}.

@item invalid-read-syntax
@code{"Invalid read syntax"}@*
@xref{Input Functions}.

@item invalid-regexp
@code{"Invalid regexp"}@*
@xref{Regular Expressions}.

@c XEmacs feature
@item mark-inactive
@code{"The mark is not active now"}@*

@item no-catch
@code{"No catch for tag"}@*
@xref{Catch and Throw}.

@c XEmacs feature
@item overflow-error
@code{"Arithmetic overflow error"}@*

@c XEmacs feature
@item protected-field
@code{"Attempt to modify a protected field"}@*

@c XEmacs feature
@item range-error
@code{"Arithmetic range error"}@*

@item search-failed
@code{"Search failed"}@*
@xref{Searching and Matching}.

@item setting-constant
@code{"Attempt to set a constant symbol"}@*
@xref{Constant Variables, , Variables that Never Change}.

@c XEmacs feature
@item singularity-error
@code{"Arithmetic singularity error"}@*

@c XEmacs feature
@item tooltalk-error
@code{"ToolTalk error"}@*
@xref{ToolTalk Support}.

@c XEmacs feature
@item undefined-keystroke-sequence
@code{"Undefined keystroke sequence"}@*

@ignore FSF Emacs only
@item undefined-color
@code{"Undefined color"}@*
@xref{Color Names}.
@end ignore

@item void-function
@code{"Symbol's function definition is void"}@*
@xref{Function Cells}.

@item void-variable
@code{"Symbol's value as variable is void"}@*
@xref{Accessing Variables}.

@item wrong-number-of-arguments
@code{"Wrong number of arguments"}@*
@xref{Classifying Lists}.

@item wrong-type-argument
@code{"Wrong type argument"}@*
@xref{Type Predicates}.
@end table

  These error types, which are all classified as special cases of
@code{arith-error}, can occur on certain systems for invalid use of
mathematical functions.

@table @code
@item domain-error
@code{"Arithmetic domain error"}@*
@xref{Math Functions}.

@item overflow-error
@code{"Arithmetic overflow error"}@*
@xref{Math Functions}.

@item range-error
@code{"Arithmetic range error"}@*
@xref{Math Functions}.

@item singularity-error
@code{"Arithmetic singularity error"}@*
@xref{Math Functions}.

@item underflow-error
@code{"Arithmetic underflow error"}@*
@xref{Math Functions}.
@end table