Implement sub-command parsing + add on/word/line/over commands

src/vm/commands/over.ts

@@ -0,0 +1,25 @@
+import {Command, CommandData, ParseContext, StrLVal} from "./command.js";
+import {Executable} from "../parse.js";
+import {LexInput} from "../lexer.js";
+
+export type OverData = {
+    subject: StrLVal,
+    exec: Executable<CommandData>,
+}
+
+export class Over extends Command<OverData> {
+    async attemptParse(context: ParseContext): Promise<OverData> {
+        return {
+            subject: context.popLVal(),
+            exec: await context.popExecutable(),
+        }
+    }
+
+    getDisplayName(): string {
+        return 'over'
+    }
+
+    isParseCandidate(token: LexInput): boolean {
+        return this.isKeyword(token, 'over')
+    }
+}