Indeed. Consider https://github.com/chadaustin/buffer-builder/blob/master/src/Data/BufferBuilder.hs#L164 https://github.com/chadaustin/buffer-builder/blob/mast

Indeed. Consider https://github.com/chadaustin/buffer-builder/blob/master/src/Data/BufferBuilder.hs#L164 https://github.com/chadaustin/buffer-builder/blob/master/src... The API is pure, but it's implemented with a high-performance effectful monad, and none of the implementation details are exported. A perfect use of unsafe[Dupable]PerformIO.