Added support for Racket (#2315)

Author: RunDevelopment

components.js

@@ -866,6 +866,12 @@
 			"title": "R",
 			"owner": "Golmote"
 		},
+		"racket": {
+			"title": "Racket",
+			"require": "scheme",
+			"alias": "rkt",
+			"owner": "RunDevelopment"
+		},
 		"jsx": {
 			"title": "React JSX",
 			"require": ["markup", "javascript"],

components.json

@@ -0,0 +1,58 @@
+Prism.languages.racket = Prism.languages.extend('scheme', {});
+
+// Add brackets to racket
+// The basic idea here is to go through all pattens of Scheme and replace all occurrences of "(" with the union of "("
+// and "["; Similar for ")". This is a bit tricky because "(" can be escaped or inside a character set. Both cases
+// have to be handled differently and, of course, we don't want to destroy groups, so we can only replace literal "("
+// and ")".
+// To do this, we use a regular expression which will parse any JS regular expression. It works because regexes are
+// matches from left to right and already matched text cannot be matched again. We use this to first capture all
+// escaped characters (not really, we don't get escape sequences but we don't need them). Because we already captured
+// all escaped characters, we know that any "[" character is the start of a character set, so we match that character
+// set whole.
+// With the regex parsed, we only have to replace all escaped "(" (they cannot be unescaped outside of character sets)
+// with /[([]/ and replace all "(" inside character sets.
+// Note: This method does not work for "(" that are escaped like this /\x28/ or this /\u0028/.
+Prism.languages.DFS(Prism.languages.racket, function (key, value) {
+	if (Prism.util.type(value) === 'RegExp') {
+		var source = value.source.replace(/\\(.)|\[\^?((?:\\.|[^\\\]])*)\]/g, function (m, g1, g2) {
+			if (g1) {
+				if (g1 === '(') {
+					// replace all '(' characters outside character sets
+					return '[([]';
+				}
+				if (g1 === ')') {
+					// replace all ')' characters outside character sets
+					return '[)\\]]';
+				}
+			}
+			if (g2) {
+				var prefix = m[1] === '^' ? '[^' : '[';
+				return prefix + g2.replace(/\\(.)|[()]/g, function (m, g1) {
+					if (m === '(' || g1 === '(') {
+						// replace all '(' characters inside character sets
+						return '([';
+					}
+					if (m === ')' || g1 === ')') {
+						// replace all ')' characters inside character sets
+						return ')\\]';
+					}
+					return m;
+				}) + ']';
+			}
+			return m;
+		});
+
+		this[key] = RegExp(source, value.flags);
+	}
+});
+
+Prism.languages.insertBefore('racket', 'string', {
+	'lang': {
+		pattern: /^#lang.+/m,
+		greedy: true,
+		alias: 'keyword'
+	}
+});
+
+Prism.languages.rkt = Prism.languages.racket;

components/prism-racket.js

@@ -0,0 +1,16 @@
+<h2>Full example</h2>
+<pre><code>; Source: https://github.com/mbutterick/pollen/blob/master/pollen/private/to-string.rkt
+
+#lang racket/base
+(provide (all-defined-out))
+
+(define (to-string x)
+  (cond
+    [(string? x) x]
+    [(or (null? x) (void? x)) ""]
+    [(or (symbol? x) (number? x) (path? x) (char? x)) (format "~a" x)]
+    ;; special handling for procedures, because if a procedure reaches this func,
+    ;; it usually indicates a failed attempt to use a tag function.
+    ;; meaning, it's more useful to raise an error.
+    [(procedure? x) (error 'pollen "Can't convert procedure ~a to string" x)]
+    [else (format "~v" x)]))</code></pre>

components/prism-racket.min.js

@@ -97,6 +97,7 @@
 		],
 		"qml": "javascript",
 		"qore": "clike",
+		"racket": "scheme",
 		"jsx": [
 			"markup",
 			"javascript"
@@ -181,6 +182,7 @@
 		"pq": "powerquery",
 		"mscript": "powerquery",
 		"py": "python",
+		"rkt": "racket",
 		"robot": "robotframework",
 		"rb": "ruby",
 		"sln": "solution-file",

examples/prism-racket.html

@@ -136,6 +136,7 @@
 		"py": "Python",
 		"q": "Q (kdb+ database)",
 		"qml": "QML",
+		"rkt": "Racket",
 		"jsx": "React JSX",
 		"tsx": "React TSX",
 		"renpy": "Ren'py",