Macros are the single greatest advantage that lisp has as a programming language and the single greatest advantage of any programming language. With them you can do things that you simply cannot do in other languages. Because macros can be used to transform lisp into other programming languages and back, programmers who gain experience with them discover that all other languages are just skins on top of lisp. This is the big deal. Lisp is special because programming with it is actually programing at a higher level. Where most languages invent and enforce syntactic and semantic rules, lisp is general and malleable. With lisp, you make the rules.
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Understanding why macros are so great requires understanding what lisp has that other languages don't. It requires an understanding of other, less powerful languages. Sadly, most programmers lose the will to learn after they have mastered a few other languages and never make it close to understanding what a macro is or how to take advantage of one. But the top percentile of programmers in any language are always forced to learn some sort of way to write programs that write programs: macros. Because it is the best language for writing macros, the smartest and most determined and most curious programmers always end up at lisp.
An interesting parallel to learning macros in Lisp and the FORTRAN-in-any-language symptom!
An interesting parallel to learning macros in lisp is that of learning pointers in the C programming language. Most beginning C programmers are able to quickly pick up most of the language. Functions, types, variables, arithmetic expressions: all have parallels in previous intellectual experiences beginners might have had, from elementary school maths to experimenting with simpler programming languages. But most novice C programmers hit a brick wall when they encounter pointers.
Pointers are second nature to experienced C programmers, most of whom consider their complete understanding necessary for the proper use of C. Because pointers are so fundamental, most experienced C programmers would not advise limits on their use for stylistic or learning purposes. Despite this, many C novices feel pointers are an unnecessary complication and avoid their use, resulting in the FORTRAN-in-any-language symptom where valuable language feature