Implemented step 2.

src/step0_repl.ts

@@ -0,0 +1,25 @@
+import {readUserInputs} from "./shared.ts";
+
+function read(source: string): string {
+    return source;
+}
+
+function eval_(ast: string): string {
+    return ast;
+}
+
+function print(form: string): string {
+    return form
+}
+
+function rep(source: string): string{
+    return print(eval_(read( source)))
+}
+
+
+
+export function main(): void {
+     for(const userInput of readUserInputs()){
+         rep(userInput);
+     }
+}