Trie-regexes

Regexes, but neater and more cumbersome
Say you wanted to use regex to find matches of any valid CSS color names in some source haystack of text - as people often do, I'm sure. Considering that the list is pretty fukken big, and your time is precious, you would probably just multiline-edit the list in your code editor into a simple regex.

So something like that ^ turns into something like this v

/(aliceblue|antiquewhite|aqua|aquamarine|azure|beige|bisque|black|blanchedalmond|blue|blueviolet|brown|burlywood|cadetblue|chartreuse|chocolate|coral|cornflowerblue|cornsilk|crimson|cyan|darkblue|darkcyan|darkgoldenrod|darkgray|darkgrey|darkgreen|darkkhaki|darkmagenta|darkolivegreen|darkorange|darkorchid|darkred|darksalmon|darkseagreen|darkslateblue|darkslategray|darkslategrey|darkturquoise|darkviolet|deeppink|deepskyblue|dimgray|dimgrey|dodgerblue|firebrick|floralwhite|forestgreen|fuchsia|gainsboro|ghostwhite|gold|goldenrod|gray|grey|green|greenyellow|honeydew|hotpink|indianred|indigo|ivory|khaki|lavender|lavenderblush|lawngreen|lemonchiffon|lightblue|lightcoral|lightcyan|lightgoldenrodyellow|lightgray|lightgrey|lightgreen|lightpink|lightsalmon|lightseagreen|lightskyblue|lightslateblue|lightslategray|lightslategrey|lightsteelblue|lightyellow|lime|limegreen|linen|magenta|maroon|mediumaquamarine|mediumblue|mediumorchid|mediumpurple|mediumseagreen|mediumslateblue|mediumspringgreen|mediumturquoise|mediumvioletred|midnightblue|mintcream|mistyrose|moccasin|navajowhite|navy|oldlace|olive|olivedrab|orange|orangered|orchid|palegoldenrod|palegreen|paleturquoise|palevioletred|papayawhip|peachpuff|peru|pink|plum|powderblue|purple|rebeccapurple|red|rosybrown|royalblue|saddlebrown|salmon|sandybrown|seagreen|seashell|sienna|silver|skyblue|slateblue|slategray|slategrey|snow|springgreen|steelblue|tan|teal|thistle|tomato|transparent|turquoise|violet|wheat|white|whitesmoke|yellow|yellowgreen)/i

That'll definitely work just fine, and is quite simple and fast to write even by hand. But what you gain in ease-of-creation, you lose in performance and length. Given a large enough set of words, this naïve pattern could easily end up biting you in the ass. Another option would be to organize the pattern into a Trie-structure aka. a prefix tree, like so:

/^(
	a(liceblue|ntiquewhite|qua(marine)?|zure)|
	b(eige|isque|l(a(ck|nchedalmond)|ue(violet)?)|rown|urlywood)|
	c(adetblue|h(artreuse|ocolate)|or(al|n(flowerblue|silk))|rimson|yan)|
	d(ark(blue|cyan|g(oldenrod|r(ay|e(en|y)))|khaki|magenta|o(livegreen|r(ange|chid))|red|s(almon|eagreen|late(blue|gr[ae]y))|turquoise|violet)|eep(pink|skyblue)|imgr[ae]y|odgerblue)|
	f(irebrick|loralwhite|orestgreen|uchsia)|
	g(ainsboro|hostwhite|old(enrod)?|r(ay|e(en(yellow)?|y)))|
	ho(neydew|tpink)|
	i(n(dianred|digo)|vory)|
	khaki|
	l(a(vender(blush)?|wngreen)|emonchiffon|i(ght(blue|coral|cyan|g(oldenrodyellow|r(ay|e(en|y)))|pink|s(almon|eagreen|kyblue|lategr[ae]y|teelblue)|yellow)|me(green)?|nen))|
	m(a(genta|roon)|edium(aquamarine|blue|orchid|purple|s(eagreen|lateblue|pringgreen)|turquoise|violetred)|i(dnightblue|ntcream|styrose)|occasin)|
	nav(ajowhite|y)|
	o(l(dlace|ive(drab)?)|r(ange(red)?|chid))|
	p(a(le(goldenrod|green|turquoise|violetred)|payawhip)|e(achpuff|ru)|ink|lum|owderblue|urple)|
	r(e(beccapurple|d)|o(sybrown|yalblue))|
	s(a(ddlebrown|lmon|ndybrown)|ea(green|shell)|i(enna|lver)|kyblue|late(blue|gr[ae]y)|now|pringgreen|teelblue)|
	t(an|eal|histle|omato|urquoise)|
	violet|
	wh(eat|ite(smoke)?)|
	yellow(green)?
)$/i

Formatted with whitespace for readability

Basically, instead of listing each word in its entirety as a flat list in the pattern, you create capture groups of the words based on their alphabetical prefixes. Now, granted, I doubt many people would opt to create these sorts of patterns by hand. So the trie-based patterns definitely cause a bit more friction for the developer during the pattern creation. But apparently these are a shit-ton faster to execute, and usually end up a lot shorter. With the color names I used here as an example, the naïve pattern is 1501 characters long, while the triegex ended up being just 1185 characters. I'm not mathematician, but I do believe that's a solid third less wasted space. Ain't that dank.