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The problem for me is that I've learned to avoid macros in other languages. It seems to me that when you've got a fairly complex program, you need a fairly comp

The problem for me is that I've learned to avoid macros in other languages. It seems to me that when you've got a fairly complex program, you need a fairly complex mental model of what the program "is" to understand it. But if you introduce macros, or code writing code, then you have a much more complex mental model since now even what the code "is" can change. What is it about lisp that makes this an easier sell?

reikonomusha 9y ago
When the "atoms" of your language are causing whatever problem you're solving to be difficult to express, then it may be wise to introduce new "atoms" to make the idea easier to express. The new atoms are supposed to communicate intent faster and more concisely, and decrease the burden of understanding what's going on. That's the role of an abstraction, especially syntactic abstractions.
willismichael 9y ago
It is true that even in a Lisp, unfettered use of macros can result in write-only code, so you do have to be careful about what kind of cognitive burden you are imposing upon people who will have to read your code. With that said, I tried to learn about metaprogramming in a number of other languages, and Lisp is the first one with a metaprogramming model that I could actually grok, because the meta-language is equivilant to the language itself. Lisp macros are more or less just plain old code that manipulates data structures. When I'm working on a lisp project, I give myself a budget of a very small number (often just 1 or 2) of magic macros that I can build for it. Other than that, I only use macros in the core library, or well-known third party libraries that other people are likely to be familiar with.
flavio81 9y ago
>The problem for me is that I've learned to avoid macros in other languages. Macros in other languages are significntly unlike Lisp macros. You should take a look at the Practical Common Lisp book (available for free online) to have an idea on how you can easily leverage Lisp macros for more readable, succint, easy to understand code. >But if you introduce macros, or code writing code, then you have a much more complex mental model In Lisp, you use the different tools available (macros, CLOS, readtables, etc) to achieve a simpler translation between the problem domain and your actual source code. If you are using them to create more convoluted, harder-to-understand code, then "you're doing it wrong", just as you can, for example, write rather clean C code versus code that would win the IOCCC (International Obfuscated C Code Competition).
- qohen 9y ago
  Another free Lisp book, one that focuses on macros -- and is quite readable -- is YC-founder Paul Graham's "On Lisp". There's a download page [0] (for the book and code) at paulgraham.com as well as the following on a description page [1]: On Lisp is a comprehensive study of advanced Lisp techniques, with bottom-up programming as the unifying theme. It gives the first complete description of macros and macro applications. The book also covers important subjects related to bottom-up programming, including functional programming, rapid prototyping, interactive development, and embedded languages. The final chapter takes a deeper look at object-oriented programming than previous Lisp books, showing the step-by-step construction of a working model of the Common Lisp Object System (CLOS). As well as an indispensable reference, On Lisp is a source of software. Its examples form a library of functions and macros that readers will be able to use in their own Lisp programs. [0] http://www.paulgraham.com/onlisptext.html http://www.paulgraham.com/onlisptext.html [1] http://www.paulgraham.com/onlisp.html http://www.paulgraham.com/onlisp.html

reikonomusha 9y ago

When the "atoms" of your language are causing whatever problem you're solving to be difficult to express, then it may be wise to introduce new "atoms" to make the idea easier to express. The new atoms are supposed to communicate intent faster and more concisely, and decrease the burden of understanding what's going on. That's the role of an abstraction, especially syntactic abstractions.

willismichael 9y ago

It is true that even in a Lisp, unfettered use of macros can result in write-only code, so you do have to be careful about what kind of cognitive burden you are imposing upon people who will have to read your code. With that said, I tried to learn about metaprogramming in a number of other languages, and Lisp is the first one with a metaprogramming model that I could actually grok, because the meta-language is equivilant to the language itself. Lisp macros are more or less just plain old code that manipulates data structures. When I'm working on a lisp project, I give myself a budget of a very small number (often just 1 or 2) of magic macros that I can build for it. Other than that, I only use macros in the core library, or well-known third party libraries that other people are likely to be familiar with.

flavio81 9y ago

>The problem for me is that I've learned to avoid macros in other languages. Macros in other languages are significntly unlike Lisp macros. You should take a look at the Practical Common Lisp book (available for free online) to have an idea on how you can easily leverage Lisp macros for more readable, succint, easy to understand code. >But if you introduce macros, or code writing code, then you have a much more complex mental model In Lisp, you use the different tools available (macros, CLOS, readtables, etc) to achieve a simpler translation between the problem domain and your actual source code. If you are using them to create more convoluted, harder-to-understand code, then "you're doing it wrong", just as you can, for example, write rather clean C code versus code that would win the IOCCC (International Obfuscated C Code Competition).

qohen 9y ago
Another free Lisp book, one that focuses on macros -- and is quite readable -- is YC-founder Paul Graham's "On Lisp". There's a download page [0] (for the book and code) at paulgraham.com as well as the following on a description page [1]: On Lisp is a comprehensive study of advanced Lisp techniques, with bottom-up programming as the unifying theme. It gives the first complete description of macros and macro applications. The book also covers important subjects related to bottom-up programming, including functional programming, rapid prototyping, interactive development, and embedded languages. The final chapter takes a deeper look at object-oriented programming than previous Lisp books, showing the step-by-step construction of a working model of the Common Lisp Object System (CLOS). As well as an indispensable reference, On Lisp is a source of software. Its examples form a library of functions and macros that readers will be able to use in their own Lisp programs. [0] http://www.paulgraham.com/onlisptext.html http://www.paulgraham.com/onlisptext.html [1] http://www.paulgraham.com/onlisp.html http://www.paulgraham.com/onlisp.html