Crude first pass at playground page

playground/src/monarch.ts

@@ -0,0 +1,67 @@
+import * as monaco from 'monaco-editor'
+
+export let newtLanguage: monaco.languages.IMonarchLanguage = {
+  // Set defaultToken to invalid to see what you do not tokenize yet
+  // defaultToken: 'invalid',
+
+  keywords: [
+    "let",
+    "in",
+    "where",
+    "case",
+    "of",
+    "data",
+    "U",
+    "module",
+    "ptype",
+    "pfunc",
+    "module",
+    "infixl",
+    "infixr",
+    "infix",
+  ],
+  specialOps: ["=>", "->", ":", "=", ":="],
+  tokenizer: {
+    root: [
+      [
+        /[a-z_$][\w$]*/,
+        { cases: { "@keywords": "keyword", "@default": "identifier" } },
+      ],
+      [/[A-Z][\w\$]*/, "type.identifier"],
+      [/\\|λ/, "keyword"],
+      { include: "@whitespace" },
+      [/[{}()\[\]]/, "@brackets"],
+      [
+        /[:!#$%&*+.<=>?@\\^|~\/-]+/,
+        {
+          cases: {
+            "@specialOps": "keyword",
+            "@default": "operator",
+          },
+        },
+      ],
+
+      [/\d+/, "number"],
+
+      // strings
+      [/"([^"\\]|\\.)*$/, "string.invalid"], // non-teminated string
+      [/"/, { token: "string.quote", bracket: "@open", next: "@string" }],
+    ],
+    comment: [
+      [/[^-]+/, "comment"],
+      ["-/", "comment", "@pop"],
+      ["-", "comment"],
+    ],
+    string: [
+      [/[^\\"]+/, "string"],
+      // [/@escapes/, "string.escape"],
+      [/\\./, "string.escape.invalid"],
+      [/"/, { token: "string.quote", bracket: "@close", next: "@pop" }],
+    ],
+    whitespace: [
+      [/[ \t\r\n]+/, "white"],
+      ["/-", "comment", "@comment"],
+      [/--.*$/, "comment"],
+    ],
+  },
+};