We have added new material to Chapter 3 to give an account of up-to-date programming techniques using accumulators and difference structures.
Chapter 8 contains some new information on syntax errors. Operator
precedences are now compatible with the most widely-used implementations.
We have made further reorganisations and improvements in presentation,
and have corrected a number of minor errors. We thank the many people
who brought typographical errors in the previous edition to our attention,
and we thank A.R.C. for careful proofreading.