Abstract
As functional programmers, we are comfortable with the idea of mapping a function across the members of a list to obtain a new list of values. But there are very similar ways of mapping functions across other kinds of data structure, so what is special about lists? Why can’t we use the same name for each of these functions leaving the type system to determine which is appropriate in a particular situation? This is not just a matter of aesthetics or syntax since it would allow us to write general functions for any data structure that has an associated map function without having to repeat essentially the same definition in each case.
This paper describes a system of overloading based on the use of constructor classes — a natural generalization of type classes in Haskell — which provides a satisfactory solution to this problem and appears to have many other useful applications. We illustrate this with some examples using Wadler’s monadic style of programming, including the first concrete implementation of monad comprehensions known to us at the time of writing.
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© 1993 British Computer Society
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Jones, M.P. (1993). Programming with Constructor Classes (preliminary summary). In: Launchbury, J., Sansom, P. (eds) Functional Programming, Glasgow 1992. Workshops in Computing. Springer, London. https://doi.org/10.1007/978-1-4471-3215-8_11
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DOI: https://doi.org/10.1007/978-1-4471-3215-8_11
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