Reasoning about a macro is no harder than reasoning about a higher-order function: you reason about the macro function (which is a simple transformation on some

Reasoning about a macro is no harder than reasoning about a higher-order function: you reason about the macro function (which is a simple transformation on some tree data structure), and the generated function. Except that C-style macro functions aren't "simple transformations on some tree data structure". They are textual transformations. Hygienic macros (à la Racket) I agree are useful and easy to reason about. I wouldn't use Javascript and Python as examples here--those languages, suffering from their lack of meta-programming, instead encourage heinous things like monkey-patching and runtime introspection, which are insanely difficult to reason about. I agree that the mechanism underlying their meta-programming facilities is treacherous. What I mean (and didn't state clearly) is that over the decades, these languages have developed patterns for reining in the power of their facilities (decorators in Python, and a fairly standard pattern for emulating class-bassed OO in Javascript).