Filtering Unique Items from Heterogeneous Lists at Compile Time

A deep dive into Haskell type-level programming, showing how to build heterogeneous lists (HList), reverse them, and filter out duplicate types at compile time. The post walks through defining GADTs, type families (Reverse, Contains, If, Uniques), and type classes with accumulator patterns to implement a compile-time unique-filter function. It bridges the gap between introductory HList tutorials and advanced library usage, explaining the reasoning behind class constraints, type applications, and the ContainsHead helper.