Debugging hygienic macros

13 years 2 months ago

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Over the past two decades, Scheme macros have evolved into a powerful API for the compiler front-end. Like Lisp macros, their predecessors, Scheme macros expand source programs into a small core language; unlike Lisp systems, Scheme macro expanders preserve lexical scoping, and advanced Scheme macro systems handle other important properties such as source location. Using such macros, Scheme programmers now routinely develop the ultimate ion: embedded domain-speciﬁc programming languages. Unfortunately, a typical Scheme programming environment provides little support for macro development. This lack makes it diﬃcult for programmers to debug their macros and for novices to study the behavior of macros. In response, we have developed a stepping debugger specialized to the concerns of macro expansion. This debugger presents the macro expansion process as a linear rewriting sequence of annotated terms; it graphically illustrates the structure of the program as expansion reveals it; and...

Ryan Culpepper, Matthias Felleisen

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