Add TeX/LaTeX support.

Fixes #88.

lexers/tex.go

@@ -0,0 +1,55 @@
+package lexers
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+)
+
+// Tex lexer.
+var TeX = Register(MustNewLexer(
+	&Config{
+		Name:      "TeX",
+		Aliases:   []string{"tex", "latex"},
+		Filenames: []string{"*.tex", "*.aux", "*.toc"},
+		MimeTypes: []string{"text/x-tex", "text/x-latex"},
+	},
+	Rules{
+		"general": {
+			{`%.*?\n`, Comment, nil},
+			{`[{}]`, NameBuiltin, nil},
+			{`[&_^]`, NameBuiltin, nil},
+		},
+		"root": {
+			{`\\\[`, LiteralStringBacktick, Push("displaymath")},
+			{`\\\(`, LiteralString, Push("inlinemath")},
+			{`\$\$`, LiteralStringBacktick, Push("displaymath")},
+			{`\$`, LiteralString, Push("inlinemath")},
+			{`\\([a-zA-Z]+|.)`, Keyword, Push("command")},
+			{`\\$`, Keyword, nil},
+			Include("general"),
+			{`[^\\$%&_^{}]+`, Text, nil},
+		},
+		"math": {
+			{`\\([a-zA-Z]+|.)`, NameVariable, nil},
+			Include("general"),
+			{`[0-9]+`, LiteralNumber, nil},
+			{`[-=!+*/()\[\]]`, Operator, nil},
+			{`[^=!+*/()\[\]\\$%&_^{}0-9-]+`, NameBuiltin, nil},
+		},
+		"inlinemath": {
+			{`\\\)`, LiteralString, Pop(1)},
+			{`\$`, LiteralString, Pop(1)},
+			Include("math"),
+		},
+		"displaymath": {
+			{`\\\]`, LiteralString, Pop(1)},
+			{`\$\$`, LiteralString, Pop(1)},
+			{`\$`, NameBuiltin, nil},
+			Include("math"),
+		},
+		"command": {
+			{`\[.*?\]`, NameAttribute, nil},
+			{`\*`, Keyword, nil},
+			Default(Pop(1)),
+		},
+	},
+))