Table of Contents generated with autotoc
ht.el
The missing hash table library for Emacs.
Functions
Return a hash table
ht-create
(test?)
ht-merge
(&rest tables)
ht-copy
(table)
ht-select
(function table)
ht-reject
(function table)
Accessing the hash table
ht-get
(table key default?)
ht-keys
(table)
ht-values
(table)
ht-items
(table)
ht-find
(function table)
ht-size
(table)
Mutating the hash table
ht-set!
(table key value)
ht-update!
(table table)
ht-remove!
(table key)
ht-clear!
(table)
ht-reject!
(function table)
Iterating over the hash table
ht-map
(function table)
ht-each
(function table)
Predicates
ht?
(table-or-object)
ht-contains?
(table key)
ht-empty?
(table)
Converting from a hash table
ht->alist
(table)
ht->plist
(table)
Converting to a hash table
ht<-alist
(alist)
ht<-plist
(plist)
Macros
Returning a hash table
ht
(&rest pairs)
Iterating over the hash table (anaphoric)
ht-amap
(form table)
ht-aeach
(form table)
Examples
Creating a hash table and accessing it:
(require 'ht)
(defun say-hello (name)
(let ((greetings (ht ("Bob" "Hey bob!")
("Chris" "Hi Chris!"))))
(ht-get greetings name "Hello stranger!")))
This could be alternatively written as:
(require 'ht)
(defun say-hello (name)
(let ((greetings (ht-create)))
(ht-set! greetings "Bob" "Hey Bob!")
(ht-set! greetings "Chris" "Hi Chris!")
(ht-get greetings name "Hello stranger!")))
Why?
Libraries like s.el (strings) and dash.el (lists) have shown how much nicer Emacs lisp programming can be with good libraries. ht.el aims to similarly simplify working with hash tables.
Common operations with hash tables (e.g. enumerate the keys) are too difficult in Emacs lisp.
ht.el offers:
- A consistent naming scheme (contrast
make-hash-table
withputhash
) - A more natural argument ordering
- Mutation functions always return
nil
- A more comprehensive range of hash table operations, including a
conventional map (
ht-map
returns a list, elisp'smaphash
returns nil).
Similar libraries
- kv.el (focuses more on alists)
- mon-hash-utils
Installation
ht.el is availabe on MELPA and Marmalade.
Add a package archive to your .emacs.d/init.el:
(require 'package)
(add-to-list 'package-archives '("melpa" . "http://melpa.milkbox.net/packages/") t)
then run M-x package-install <RET> ht <RET>
Changelog
ht.el uses semantic versioning, so an incompatible API change will result in the major version increasing. See CHANGELOG.md for a history of all changes.
Running tests
M-x ht-run-tests
What's an alist/plist?
An alist is an association list, which is a list of pairs. It looks like this:
((key1 . value1)
(key2 . value2)
(key3 . value3))
An alist can also look like this:
((key1 . value1)
(key2 . value2)
(key1 . oldvalue))
A plist is a property list, which is a flat list with an even number of items. It looks like this:
(key1 value1
key2 value2
key3 value3)
Both of these are slow. ht.el provides ht<-alist
and
ht<-plist
to help you convert to hash tables. If you need to
work with an alist or plist, use the functions ht->alist
and
ht->plist
to convert an hash table to those formats.