Notes on Compatibility

The sample programs rely on the Standard ML Basis Library.

Starting with Chapter 7, they also rely (to a minor extent) on recent changes to ML itself. I am distributing the code in a form suitable for use with up-to-date ML compilers. Older compilers (pre-1998) might be incompatible in three respects:

• Instead of Real.==(x,y), they might use x=y to test equality on real numbers. This affects code for Chapter 3.
• Instead of value polymorphism, they might have weak (imperative) type variables such as '_a. (Chapters 8 and 10.)
• Instead of the :> syntax, they might use the abstraction keyword to indicate opaque signature constraints. (Chapters 8 and 10.)

Alternative versions of the programs for chapters 3, 8 and 10 are provided for use with older compilers.

Later chapters sometimes refer to code presented in earlier chapters. However, if you compile the code for all the chapters in order, there should be no compilation errors.

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