Of all modern programming languages, Standard ML has ascribed perhaps the highest priority to rigorous semantic definition. It is therefore the preferred language for many applications where rigor is important; this is notably true of tools for formal program analysis. It has also gained users who value its high degree of portability, a direct consequence of the unambiguity of its definition.

Now Emden Gansner and John Reppy have equipped SML with another essential ingredient: a library of signatures, structures, and functors which will greatly ease the programmer's task. The SML Basis Library has been long in gestation, but this has ensured that it contains the right things. Only by close cooperation with users, over a considerable period of time, can one be sure of consistency and balance in defining a library. We can therefore be confident that the Basis Library will bring SML into still wider use, and we owe warm thanks to its creators for undertaking an arduous task with skill, care, and dedication.