Data commit

Task/Menu/D/menu.d

@@ -0,0 +1,35 @@
+import std.stdio, std.conv, std.string, std.array, std.typecons;
+
+string menuSelect(in string[] entries) {
+    static Nullable!(int, -1) validChoice(in string input,
+                                          in int nEntries)
+    pure nothrow {
+        try {
+            immutable n = input.to!int;
+            return typeof(return)((n >= 0 && n <= nEntries) ? n : -1);
+        } catch (Exception e) // Very generic
+            return typeof(return)(-1); // Not valid.
+    }
+
+    if (entries.empty)
+        return "";
+
+    while (true) {
+        "Choose one:".writeln;
+        foreach (immutable i, const entry; entries)
+            writefln("  %d) %s", i, entry);
+        "> ".write;
+        immutable input = readln.chomp;
+        immutable choice = validChoice(input, entries.length - 1);
+        if (choice.isNull)
+            "Wrong choice.".writeln;
+        else
+            return entries[choice]; // We have a valid choice.
+    }
+}
+
+void main() {
+    immutable items = ["fee fie", "huff and puff",
+                       "mirror mirror", "tick tock"];
+    writeln("You chose '", items.menuSelect, "'.");
+}