Just curious, what lisp is good for and what lisp is not the best choice?
I was thinking about what the hello-world of Lisp macros is. It might be something like (mac hello (x) `(set ,x t)) This takes one argument and sets it to t. > (hello foo) t > foo t
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It's particularly good for exploratory programming, meaning when you're solving problems you don't understand yet. (Which actually is most programming.) It might not be so good for very low-level C-type programming where you're manipulating specific bytes in memory.
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In what circumstances is it better to use a macro v using a function ?
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You should only use a macro to do something you can't do with a function.
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i've always liked this first example from https://www.braveclojure.com/writing-macros/ pic.twitter.com/jOqWHSLBxO
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Not quite hello world, but one of my favorite beginner macros, to demonstrate the power of lisp, is nullthrows. Helps grasp the concept that the argument is the ast
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(defmacro nil-throws [form] `(let [result# ~form] (if (nil? result#) (throw (ex-info "uh oh, we got nil!" {:form '~form})) result#)))
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I just started learning Lisp & found this helpful to understand macros (.clj -> .cl): (defmacro echo (e) `(progn ,e ,e)) This takes one argument and “runs” it twice. > (echo (format t "hello ")) hello hello NIL in contrast: > (defun…) (PROGN NIL NIL)https://stackoverflow.com/questions/3667403/what-is-the-difference-between-defn-and-defmacro …
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@paulg what about this macro? (defmacro pass-args (code &rest args) `(,@code ,@args)) It takes one argument and “applies” it to the others. > (pass-args (format) t "Hello, World!") Hello, World! NIL > (pass-args (+) 1 2 3) 6 Thanks for the challenge! https://gist.github.com/jorgezaccaro/55cb80fdf939586db58a450c0d87a1a9 … -
Can you give an example where you use this macro to write something that would be inconvenient to write without it?
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