The first high-level languages developed for general purpose programming were Fortran (Backus, 1978) and Lisp (McCarthy, 1978), developed in the late 1950s by John Backus and John McCarthy, respectively. From Fortran grew many of today's modern imperative languages, most of which did not improve significantly on the fundamental ideas found in the language Algol (de Morgan, Hill and Wichmann, 1976), which shortly followed Fortran. The Lisp family was less fecund, perhaps because it was so far ahead of its time, but was the seed for the family of functional languages about which this textbook was written. The most radical in this class of languages is probably Haskell, originally designed in the late 1980s (Hudak, Wadler, 1988) based on, at that point, a good ten years of experience designing and implementing similar languages, most notably a series of languages developed by David Turner in the late 1970s and early 1980s (Turner, 1976; 1985). Although research continues on the design of Haskell, the version used in this textbook, Haskell 98 (Augustsson, et al., 1999), is the latest and most stable version of the language and its libraries.

Haskell was named after the logician Haskell B. Curry who, along with Alonzo Church, established the theoretical foundations of functional programming back when computers themselves were only a gleam in researchers' eyes. A curious historical fact is that Haskell Curry's father, Samuel Silas Curry, helped to found and direct a school in Boston called the School of Expression. Because pure functional programming centers around the notion of an expression, I thought that The Haskell School of Expression would be a good title for this book.

A Brief Account of Language Success Stories

It's hard to predict just how it is that a language becomes popular. Fortran became popular because it was the first high-level language and a welcome alternative to assembly language, and ultimately because it was a good vehicle for coding numerical algorithms in the domain of scientific computing.