SRFI 122: Nonempty Intervals and Generalized Arrays

by Bradley J. Lucier

status: final (2016/12/24)

Abstract

This SRFI specifies an array mechanism for Scheme. Arrays as defined here are quite general; at their most basic, an array is simply a mapping, or function, from multi-indices of exact integers $i_0,\ldots,i_{d-1}$ to Scheme values. The set of multi-indices $i_0,\ldots,i_{d-1}$ that are valid for a given array form the domain of the array. In this SRFI, each array's domain consists of a rectangular interval $[l_0,u_0)\times[l_1,u_1)\times\cdots\times[l_{d-1},u_{d-1})$, a subset of $\mathbb Z^d$, $d$-tuples of integers. Thus, we introduce a data type called intervals, which encapsulate the cross product of nonempty intervals of exact integers. Specialized variants of arrays are specified to provide portable programs with efficient representations for common use cases.