This function tests whether a given key is present in a hash table.
Emacs Lisp has long lacked a standard way to do this, leading users to
write one of:
(not (eq (gethash key table 'missing) 'missing))
or
(gethash key table)
This idiom is error-prone (when 'missing' or 'nil' are valid values),
and it obscures intent. The new function avoids such pitfalls,
improves readability, and makes the intent explicit:
(hash-table-contains-p key table)
The name 'hash-table-contains-p' exists in other Lisp dialects (e.g.,
SRFI-125), and follows the precedent of 'seq-contains-p'. Other
alternatives considered include `hash-table-has-key-p` and
`hash-table-key-exists-p`, but none were clearly better.
This was previously discussed in 2018, and all comments were positive,
but the proposed patch (implementing it in C) was never pushed:
https://lists.gnu.org/r/emacs-devel/2018-02/msg00424.html
* lisp/subr.el (hash-table-contains-p): New function.
* lisp/emacs-lisp/shortdoc.el (hash-table):
* doc/lispref/hash.texi (Other Hash): Document the new function.
* test/lisp/subr-tests.el (hash-table-contains-p): New test.
* doc/lispref/hash.texi (Hash Access):
* src/fns.c (Fmaphash):
Make it clear what the function passed as argument can do. Until now
these rules were unwritten, and are still unenforced.
* lisp/emacs-lisp/shortdoc.el (hash-table): Remove hash-table-size entry.
* doc/lispref/hash.texi (Other Hash):
* src/fns.c (Fhash_table_size): Make it clear that hash-table-size is
probably not worth using.
* doc/lispref/hash.texi (Defining Hash): Explain more about what
sxhash-equal is for and what the caveats are.
* src/fns.c (Fsxhash_eql, Fsxhash_equal): Clarify doc string.
* doc/lispref/hash.texi (Creating Hash): Note that the printed
representation doesn't necessarily create a new table (bug#23417).
* doc/lispref/lists.texi (Rearrangement): Link to Self-Evaluating
Forms to further expand upon immutability.
Following a suggestion by Stefan Monnier in:
https://lists.gnu.org/r/emacs-devel/2019-07/msg00530.html
* doc/lispref/hash.texi (Creating Hash, Defining Hash):
* src/fns.c (Fsxhash_eq, Fsxhash_eql, Fsxhash_equal, Fmake_hash_table):
Don’t insist that hash codes be fixnums, reverting
the recent doc changes to the contrary.
* src/bytecode.c (exec_byte_code): Special-case only the eq case,
as the others aren’t worth tuning now that we treat bignum hashes
like fixnums.
* src/fns.c (hashfn_user_defined): If the hash code is a bignum,
reduce its hash down to a fixnum.
* doc/lispref/hash.texi (Creating Hash, Defining Hash):
* src/fns.c (Fsxhash_eq, Fsxhash_eql, Fsxhash_equal):
Say that hashes are fixnums.
(Fmake_hash_table): Say that that an integer rehash-size
should be a fixnum.
* doc/lispref/hash.texi (Defining Hash): Say that hash and
comparison functions should be consistent and pure, and should
return quickly.
* src/alloc.c (purecopy_hash_table):
* src/fns.c (maybe_resize_hash_table, Fmake_hash_table):
(Fhash_table_rehash_size):
* src/lisp.h (struct Lisp_Hash_Table.rehash_size):
The rehash_size member of struct Lisp_Hash_Table is now a
float, not a Lisp_Object.
* src/alloc.c (purecopy_hash_table): Assign members in order.
* src/fns.c (make_hash_table): Use EMACS_INT for size and
float for rehash_size, instead of Lisp_Object for both.
All callers changed.
* src/lisp.h (DEFAULT_REHASH_SIZE): Now float, not double,
and 1 smaller.
* src/print.c (print_object): Simplify by calling
Fhash_table_rehash_size and Fhash_table_rehash_threshold.
Avoid unnecessary NILP.
Change default from 0.8 to 0.8125 so it fits in float without
rounding glitches.
* doc/lispref/hash.texi (Creating Hash):
* doc/lispref/objects.texi (Hash Table Type):
* etc/NEWS:
Document change.
* src/fns.c (make_hash_table, maybe_resize_hash_table)
(Fmake_hash_table): Threshold is now float, not double.
Be consistent about how this is rounded.
* src/lisp.h (struct Lisp_Hash_Table.rehash_threshold):
Change back to float, now that the other code rounds consistently.
(DEFAULT_REHASH_THRESHOLD): Now float 0.8125 instead of double 0.8.
The manuals often used quotes ``...'' when it is better to use @dfn or
@code or capitalized words or no quoting at all. For example, there is
no need for the `` and '' in “if a variable has one effect for
@code{nil} values and another effect for ``non-@code{nil}'' values”.
Reword the Emacs, Lisp intro, and Lisp reference manuals to eliminate
unnecessary quoting like this, and to use @dfn etc. instead when called
for (Bug#21472).
doc/lispref/windows.texi (Recombining Windows): Index subject of sections.
doc/lispref/variables.texi (Variables with Restricted Values)
(Generalized Variables): Index subject of sections.
doc/lispref/text.texi (Buffer Contents, Examining Properties)
(Changing Properties, Property Search, Substitution): Index
subject of sections.
doc/lispref/syntax.texi (Motion and Syntax, Parsing Expressions)
(Motion via Parsing, Position Parse, Control Parsing): Index
subject of sections.
doc/lispref/strings.texi (Predicates for Strings, Creating Strings)
(Modifying Strings, Text Comparison): Index subject of sections.
doc/lispref/searching.texi (Syntax of Regexps, Regexp Special)
(Regexp Functions, Regexp Functions): Index subject of sections.
doc/lispref/processes.texi (Subprocess Creation, Process Information): Index
subject of sections.
doc/lispref/positions.texi (Screen Lines): Index subject of sections.
doc/lispref/nonascii.texi (Scanning Charsets, Specifying Coding Systems):
Index subject of sections.
doc/lispref/minibuf.texi (Text from Minibuffer, Object from Minibuffer)
(Multiple Queries, Minibuffer Contents): Index subject of
sections.
doc/lispref/markers.texi (Predicates on Markers, Creating Markers)
(Information from Markers, Moving Markers): Index subject of
sections.
doc/lispref/macros.texi (Defining Macros, Problems with Macros): Index
subject of sections.
doc/lispref/loading.texi (Loading Non-ASCII, Where Defined): Index subject
of sections.
doc/lispref/lists.texi (List-related Predicates, List Variables, Setcar)
(Setcdr, Plist Access): Index subject of sections.
doc/lispref/keymaps.texi (Controlling Active Maps, Scanning Keymaps)
(Modifying Menus): Index subject of sections.
doc/lispref/help.texi (Accessing Documentation, Help Functions): Index
subject of sections.
doc/lispref/hash.texi (Hash Access): Index subject of sections.
doc/lispref/functions.texi (Core Advising Primitives)
(Advising Named Functions, Porting old advices): Index subject of
sections.
doc/lispref/frames.texi (Creating Frames, Initial Parameters)
(Position Parameters, Buffer Parameters, Minibuffers and Frames)
(Pop-Up Menus, Drag and Drop): Index subject of sections.
doc/lispref/files.texi (Visiting Functions, Kinds of Files)
(Unique File Names): Index subject of sections.
doc/lispref/display.texi (Refresh Screen, Echo Area Customization)
(Warning Variables, Warning Options, Delayed Warnings)
(Temporary Displays, Managing Overlays, Overlay Properties)
(Finding Overlays, Size of Displayed Text, Defining Faces)
(Attribute Functions, Displaying Faces, Face Remapping)
(Basic Faces, Font Lookup, Fontsets, Replacing Specs)
(Defining Images, Showing Images): Index subject of sections.
doc/lispref/debugging.texi (Debugging, Explicit Debug)
(Invoking the Debugger, Excess Open, Excess Close): Index subject
of sections.
doc/lispref/customize.texi (Defining New Types, Applying Customizations)
(Custom Themes): Index subject of sections.
doc/lispref/control.texi (Sequencing, Combining Conditions)
(Processing of Errors, Cleanups): Index subject of sections.
doc/lispref/compile.texi (Eval During Compile): Index subject of sections.
doc/lispref/commands.texi (Using Interactive, Distinguish Interactive)
(Command Loop Info, Classifying Events, Event Mod)
(Invoking the Input Method): Index subject of sections.
doc/lispref/buffers.texi (Buffer List, Buffer Gap): Index subject of sections.
doc/lispref/backups.texi (Making Backups, Numbered Backups, Backup Names)
(Reverting): Index subject of sections.
doc/lispref/abbrevs.texi (Abbrev Tables, Defining Abbrevs, Abbrev Files)
(Abbrev Expansion, Standard Abbrev Tables, Abbrev Properties)
(Abbrev Table Properties): Index subject of sections.
doc/lispref/os.texi (Time of Day, Time Conversion, Time Parsing)
(Time Calculations, Idle Timers): Index subject of sections.
* commands.texi, customize.texi, display.texi, elisp.texi, files.texi:
* frames.texi, hash.texi, internals.texi, keymaps.texi, lists.texi:
* minibuf.texi, nonascii.texi, numbers.texi, objects.texi, os.texi:
* processes.texi, streams.texi, strings.texi, text.texi:
* variables.texi, windows.texi:
Hyphenate "floating-point" iff it precedes a noun.
Reword to avoid nouns and hyphenation when that's easy.
Prefer "integer" to "integer number" and "is floating point"
to "is a floating point number".
Prefer "@minus{}" to "-" when it's a minus.
* doc/lispref/hash.texi (Other Hash): Do not mention subr-x.el functions;
reverts 2013-12-22 change.
* lisp/emacs-lisp/subr-x.el: Comment.
* etc/NEWS: Small related edits.
