One essential for the success of a general-purpose language is an accompanying standard library that is rich enough and efficient enough to support the basic, day-to-day tasks common to all programming. Libraries provide the vocabulary with which a language can be used to say something about something. Without a broad common vocabulary, a language community cannot prosper as it might.

This document presents a standard basis library for SML. It is a basis library in the sense that it concerns itself with the fundamentals: primitive types such as integers and floating-point numbers, operations requiring runtime system or compiler support, such as I/O and arrays; and ubiquitous utility types such as booleans and lists. The SML Basis Library purposefully does not cover higher-level types, such as collection types, or application-oriented APIs, such as regular expression matching. The primary reason for limiting the scope in this way is that the design space for these interfaces is large (e.g. choosing between functors and polymorphism as a parameterization mechanism) and, unlike the case with lists and arrays, we do not have many years of common practice to guide the design. It is also the case that the SML Basis Library specification is a substantial document and expanding its scope would make it unwieldy.

The primary purpose of this book is to serve as a reference manual for the Basis Library, describing as clearly and completely as possible the types, values, and modules making up the Library.