[3] [DFN[絶対値]]とは、 [N[0]] との[[距離]]の大きさです。

[4] [[実数]] [VAR[x]] の[[絶対値]] [DFN[[FENCED[|][ [VAR[x]] ][|]]][|[VAR[・]]|]] は、
次のように定義されます。

[FIG(math)[
[FENCED[|][ [VAR[x]] ][|]] = [FENCED[{][ [LINES[ [VAR[x]] if [VAR[x]] ≧ 0 ][ -[VAR[x]] if [VAR[x]] < 0 ]] ]]
]FIG]

* [CODE(JS)@en[Math.abs()]] (JavaScript)

[1]
[CITE[Exploring: Math.abs Returns a Negative Number]] <http://bmaurer.blogspot.com/2006/10/mathabs-returns-negative-number.html>
([[名無しさん]] [WEAK[2006-10-20 00:50:19 +00:00]])

* [CODE@en[abs([VAR[x]])]] (ECMAScript 仕様書算法定義)

[2] [[ES3]] 仕様書中の[[算法]]の定義で用いられている[[数学関数]]
[DFN[[CODE@en[abs([VAR[x]])]]]]
は、[VAR@en[x]] の[[絶対値]]、すなわち [VAR@en[x]] が[[負]]の時は -[VAR@en[x]]、
それ以外の時は [VAR@en[x]] を表します。

;; [CITE[ECMAScript Language Specification (HTML version)]] ([TIME[2009-04-03 04:43:48 +09:00]] 版) <http://bclary.com/2004/11/07/#a-5.2>

[5] [CITE@en['''['''selectors''']''' Remove the Selectors-specific tokens, rephrase in terms o…]]
([[tabatkins]]著, [TIME[2016-12-16 07:16:49 +09:00]])
<https://github.com/w3c/csswg-drafts/commit/52554f80bac1d05be0067fff4a05d2ec126cb41f>

[6] [CITE@en[Remove the Selectors-specific tokens, per WG resolution.]]
([[tabatkins]]著, [TIME[2016-12-16 07:14:21 +09:00]])
<https://github.com/w3c/csswg-drafts/commit/177fc30c38029740a4dfdc4721fc3aa4a8273595>

[7] [CITE@en['''['''selectors-4''']''' Why is this two tokens if '>>' isn't two tokens?]]
([[fantasai]]著, [TIME[2018-01-01 20:19:47 +09:00]])
<https://github.com/w3c/csswg-drafts/commit/b9350e895ec41faa4a0e29745f416921794f5cd1>