add generics example

generics.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+
+fn List(comptime T: type) type {
+    return struct {
+        items: []T,
+        len: usize,
+    };
+}
+
+pub fn main() void {
+    var buffer: [10]i32 = undefined;
+
+    var list = List(i32){
+        .items = &buffer,
+        .len = 0,
+    };
+
+    // the same thing with an intermediate const to make it a little bit more
+    // clear:
+    // const IntList = List(i32);
+    // var list = IntList{
+    //     .items = &buffer,
+    //     .len = 0,
+    // };
+
+    std.debug.print("{}\n", .{list.items.len});
+}