. We present an overview of a prototype system based on a functional language for developing regular array circuits. The features of a simulator, floorplanner and expression transformer are discussed and illustrated. INTRODUCTION Implementing algorithms on a regular array of processors has many advantages. Besides offering an efficient realisation of parallel structures, regular patterns of interconnections also provide an opportunity for simplifying their description and their development. Various approaches for regular array design have been proposed; examples include methods based on dependence graphs [5], recurrence equations [14], and algebraic techniques [16]. This paper presents an overview of a prototype system for regular array development. The system is based on ¯FP [15], a functional language with mechanisms for abstracting spatial and temporal iteration. These abstractions result in a succinct and precise notation for specifying designs. Moreover, the explicit representat...

This note presents a trivial transformation that can eliminate many calls of the concatenate (or “append”) operator from a program. The general form of the transformation is well known, and one of the examples, transforming the reverse function, is a classic. However, so far as I am aware, this style of transformation has not previously been systematised in the way done here. The transformation is suitable for incorporation in a compiler, and improves the asymptotic time complexity of some programs from quadratic to linear. There is a syntactic test that determines when the transformation will succeed in eliminating a concatenate operation. Section 1 describes the transformation. Section 2 presents examples. Section 3 characterises the transformation’s benefits. Section 4 describes related work. Section 5 concludes. 1 The transformation First, some notational preliminaries. We write concatenate as infix +, list construction (cons) as infix:, and the empty list as []. We write [x, y, z] as an abbreviation for x: (y: (z: [])). We will make use of the following laws: (1) [ ] + x = x (2) (x: y) + z = x: (y + z) (3) (x + y) + z = x + (y + z) Laws (1) and (2) provide a recursive definition of concatenate. Law (3) states that concatenate is associative; it may be proved from laws (1) and (2). We now describe the transformation. The key idea is that whenever an application of a function f may appear as the left argument of a concatenation, then we introduce a new function f ′ , satisfying the property