September 24th, 2017

eyes black and white

A tale of many nests

This short essay will tell you about my favorite macro, nest, discuss the modularity of syntax extension, and use the implementation of that macro as an illustration for how to use defmacro, syntax-rules and syntax-case, providing along the way a comparison between these respective macro definition systems.

Using the nest macro

When I started using Scheme as my main Lisp, the first macro I wrote was the nest macro. What macro? The nest macro. The one that in Common Lisp helps my code avoid drifting hopelessly to the right as I nest binding form inside binding form... by doing the nesting for me. To illustrate the kind of issues that I'm concerned with, consider the Common Lisp code snippet below:

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