This was on one of my set texts at University in the 1990s. I still own it (somewhere) and a few others in this series. There was a companion book by David Watt

This was on one of my set texts at University in the 1990s. I still own it (somewhere) and a few others in this series. There was a companion book by David Watt which covered the implementation of interpreters and compilers and used a small functional language that looked a little bit like Pascal, called Triangle. It was written in very plain, easy-to-understand language (and the code was simple to understand, too). I have Peyton Jones's 'The Implementation of FunctionalProgramming Languages' sitting on a shelf beside me, and I often like to look back at Bird & Wadler which is a classic, though I think I lent it to someone and never got it back.