Inthis paper we d e s cribe a Curry-like t ype system for graphs and extend it w i th uniqueness information to indicate that certain objects are only `locally accessible'. The correctness o f t ype assignment guarantees that no external access o n s u c h a n object will take place in the future. We prove that types are preserved under reduction (for both type systems) for a large class o f rewrite systems. Adding uniqueness information provid e s a s olution to two p r oblems i n i mplementations of functional languages: e cient space management and interfacing with nonfunctional operations.

We present two type systems for term graph rewriting: conventional typing and (polymorphic) uniqueness typing. The latter is introduced as a natural extension of simple algebraic and higher-order uniqueness typing. The systems are given in natural deduction style using an inductive syntax of graph denotations with familiar constructs such as let and case.The conventional system resembles traditional Curry-style typing systems in functional programming languages. Uniqueness typing extends this with reference count information. In both type systems, typing is preserved during evaluation, and types can be determined effectively. Moreover, with respect to a graph rewriting semantics, both type systems turn out to be sound.

We investigate how to create a rubric that can be used to give feedback on code quality to students in introductory programming courses. Based on an existing model of code quality and a set of preliminary design rules, we constructed a rubric and put it through several design iterations. Each iteration focused on different aspects of the rubric, and solutions to various programming assignments were used to evaluate. The rubric appears to be complete for the assignments it was tested on. We articulate additional design aspects that can be used when drafting new feedback rubrics for programming courses.

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Abstract. This paper introduces TweetNaCl, a compact reimplementation of the NaCl library, including all 25 of the NaCl functions used by applications. TweetNaCl is published on Twitter and fits into just 100 tweets; the tweets are available from anywhere, any time, in an unsuspicious way. Distribution via other social media, or even printed on a sheet of A4 paper, is also easily possible.TweetNaCl is human-readable C code; it is the smallest readable implementation of a highsecurity cryptographic library. TweetNaCl is the first cryptographic library that allows correct functionality to be verified by human auditors with reasonable effort, making it suitable for inclusion into the trusted code base of a secure computer system. TweetNaCl consists of a single C source file, accompanied by a single header file generated by a short Python script (1811 bytes). The library can be trivially integrated into a wide range of software build processes.Portability and small code size come at a loss in efficiency, but TweetNaCl is sufficiently fast for most applications. TweetNaCl's cryptographic implementations meet the same security and reliability standards as NaCl: for example, complete protection against cache-timing attacks.