Many Haskell textbooks explain the evaluation of pure functional programs as a process of stepwise rewriting using equations. However, usual implementation techniques perform program transformations that make producing the corresponding tracing evaluations difficult. This paper presents a tracing interpreter for a subset of Haskell based on the pattern matching calculus of Kahl. We start from a big-step semantics in the style of Launchbury and develop a small-step semantics in the style of Sestoft's machines. This machine is used in the implementation of a step-by-step educational interpreter. We also discuss some implementation decisions and present illustrative examples.

We present Amphibian, a simulator to experience scuba diving virtually in a terrestrial setting. While existing diving simulators mostly focus on visual and aural displays, Amphibian simulates a wider variety of sensations experienced underwater. Users rest their torso on a motion platform to feel buoyancy. Their outstretched arms and legs are placed in a suspended harness to simulate drag as they swim. An Oculus Rift head-mounted display (HMD) and a pair of headphones delineate the visual and auditory ocean scene. Additional senses simulated in Amphibian are breath motion, temperature changes, and tactile feedback through various sensors. Twelve experienced divers compared Amphibian to real-life scuba diving. We analyzed the system factors that influenced the users' sense of being there while using our simulator. We present future UI improvements for enhancing immersion in VR diving simulators.