* 仕様書

[REFS[
- [10] [CITE@en[URL Standard]] ([TIME[2016-02-15 18:33:32 +09:00]] 版) <https://url.spec.whatwg.org/#ascii-lowercase>
-[1] [CITE@en-US[Cross-Origin Resource Sharing]] ([TIME[2012-03-01 14:59:15 +09:00]] 版) <http://dvcs.w3.org/hg/cors/raw-file/tip/Overview.html#converted-to-ascii-lowercase>
- [2] [CITE@en[RFC 6455 - The WebSocket Protocol]] ([TIME[2015-03-11 20:42:50 +09:00]] 版) <http://tools.ietf.org/html/rfc6455#section-2.1>
]REFS]

* 写像

[11] [[文字列]][VAR[文字列]]の[DFN[[RUBYB[ASCII小文字化]@en[ASCII lowercase]]]]は、
[VAR[文字列]]に含まれる[[範囲]] [ [CODE(char)[U+0041]], [CODE(char)[U+005A]] ] 
の[[符号位置]]をすべて[[範囲]]
[ [CODE(char)[U+0061]], [CODE(char)[U+007A]] ]
の対応する[[符号位置]]で置き換えることをいいます [SRC[>>10]]。

;; [12] ここで「対応する」は明確に定義されていませんが、[[符号位置]]に 0x20
を加えることをいいます。

[REFS[
- [9] [CITE@en[Character mapping "irc:ascii-lowercase"]] ([TIME[2016-02-29 16:22:57 +09:00]] 版) <https://chars.suikawiki.org/map/irc%3Aascii-lowercase>
- [5] [CITE@en[Character mapping "url:ASCII-lowercase"]] ([TIME[2016-02-29 16:19:36 +09:00]] 版) <https://chars.suikawiki.org/map/url%3AASCII-lowercase>
- [6] [CITE@en[Character mapping "dom:to-ASCII-lowercase"]] ([TIME[2016-02-29 16:20:12 +09:00]] 版) <https://chars.suikawiki.org/map/dom%3Ato-ASCII-lowercase>
- [7] [CITE@en[Character mapping "html:to-ASCII-lowercase"]] ([TIME[2016-02-29 16:20:34 +09:00]] 版) <https://chars.suikawiki.org/map/html%3Ato-ASCII-lowercase>
]REFS]

* 関連

[8] [[ASCII大文字に変換]]は逆方向の[[写像]]です。

* 歴史

[3] [CITE@en[Define ASCII lowercase and use it. Fixes #42. · whatwg/url@b6b7431]]
([TIME[2015-08-15 11:27:21 +09:00]] 版)
<https://github.com/whatwg/url/commit/b6b7431d4c9c9fed7b79e1e7917b2ec7b65bff90>

[4] [CITE@en[URL Standard]]
([TIME[2015-08-15 01:54:41 +09:00]] 版)
<https://url.spec.whatwg.org/#ascii-lowercase>

[13] [CITE[MIME Sniffing Standard]] ([TIME[2016-03-05 01:29:10 +09:00]] 版) <https://mimesniff.spec.whatwg.org/#converted-to-ascii-lowercase>

[14] >>13 は [[HTML Standard]] を参照しています。


[15] [CITE@en[Editorial: start using the Infra Standard]]
([[annevk]]著, [TIME[2016-11-18 20:21:54 +09:00]])
<https://github.com/whatwg/encoding/commit/a26f76889bf393999e9caad84a3647ab09c39e09>

[16] [CITE@en[Editorial: leave ASCII case-insensitive to Infra]]
([[annevk]]著, [TIME[2016-11-18 20:39:03 +09:00]])
<https://github.com/whatwg/html/commit/5f3f27bfdf0e0139f6cf5f22508f37710d917c00>

[17] [CITE@en[Editorial: make use of the Infra Standard]]
([[annevk]]著, [TIME[2016-11-18 20:06:36 +09:00]])
<https://github.com/whatwg/dom/commit/bb2890beed2be14d2f7633ec89e2bbb88ec7fdcd>

[18] [CITE@en[Editorial: start using the Infra Standard]]
([[annevk]]著, [TIME[2016-11-21 20:23:59 +09:00]])
<https://github.com/whatwg/url/commit/9001b9be7475fdf4a7a2757b5417aa4a9f06b3b6>

[19] [CITE@en[Breaking: adjust some code point definitions]]
([[annevk]]著, [TIME[2016-11-30 22:17:47 +09:00]])
<https://github.com/whatwg/infra/commit/aa38c291fc978252751a9c9942c382e879d0985e>

[20] [CITE@en[Regression: fix the definition of ASCII lower/upper alpha]]
([[xfq]]著, [TIME[2017-01-10 22:06:06 +09:00]])
<https://github.com/whatwg/infra/commit/18bddb5fc16f0c43fc0d351d0ce9e23327d59d4d>

[21] [CITE@en[Breaking: stop treating alpha and alphanumeric as mass nouns]]
([[annevk]]著, [TIME[2017-02-04 03:52:58 +09:00]])
<https://github.com/whatwg/infra/commit/4707bf7b3d8b5b6314ee3dabd29856011eebbb00>