We describe a password generation scheme based on Markov models built from English text (specifically, Charles Dickens *A Tale Of Two Cities*). We show a (linear-running-time) bijection between random bitstrings of any desired length and generated te
xt, ensuring that all passwords are generated with equal probability. We observe that the generated passwords appear to strike a reasonable balance between memorability and security. Using the system, we get 56-bit passwords like The cusay is wither? t, rather than passwords like tQ$%Xc4Ef.
Debugging lazy functional programs poses serious challenges. In support of the stop, examine, and resume debugging style of imperative languages, some debugging tools abandon lazy evaluation. Other debuggers preserve laziness but present it in a way
that may confuse programmers because the focus of evaluation jumps around in a seemingly random manner. In this paper, we introduce a supplemental tool, the algebraic program stepper. An algebraic stepper shows computation as a mathematical calculation. Algebraic stepping could be particularly useful for novice programmers or programmers new to lazy programming. Mathematically speaking, an algebraic stepper renders computation as the standard rewriting sequence of a lazy lambda-calculus. Our novel lazy semantics introduces lazy evaluation as a form of parallel program rewriting. It represents a compromise between Launchburys store-based semantics and a simple, axiomatic description of lazy computation as sharing-via-parameters. Finally, we prove that the steppers run-time machinery correctly reconstructs the standard rewriting sequence.
