Clojure macros continue to surprise me
1–10 of 31 posts
Re: Clojure macros continue to surprise me
#2The fifth time this has been posted in just over a week... it must be a REALLY good article! :)
Re: Clojure macros continue to surprise me
#3The fifth time this has been posted in just over a week... it must be a REALLY good article! :)
My bad... the sixth time (the fifth time was under a different title).
Re: Clojure macros continue to surprise me
#4> What if our macro read the source file?
> Like, actually went to the file system, opened a file, and read its content? We already have the file name conveniently stored in file, and luckily Clojure keeps sources around.
> So this is what I ended up with:
> (defn slurp-source [file key]
Looks like a function to me (which is good).
Re: Clojure macros continue to surprise me
#5[flagged]
Re: Clojure macros continue to surprise me
#6In elixir you can run docs as (init) tests too. The doctest macro is generating the tests from the docs within the module. Maybe this might be interesting together with this article.
Re: Clojure macros continue to surprise me
#7> What if our macro read the source file? > Like, actually went to the file system, opened a file, and read its content? We already have the file name conveniently stored in file , and luckily Clojure keeps sources around. > So this is what I ended up with: > (defn slurp-source [file key] Looks like a function to me (which is good).
it can't be a function because the source is only guaranteed to be available at compile time, rather than at runtime.
Re: Clojure macros continue to surprise me
#8> What if our macro read the source file? > Like, actually went to the file system, opened a file, and read its content? We already have the file name conveniently stored in file , and luckily Clojure keeps sources around. > So this is what I ended up with: > (defn slurp-source [file key] Looks like a function to me (which is good).
it can't be a function because the source is only guaranteed to be available at compile time, rather than at runtime.
A macro is a perfectly normal function. It's simply called at compile time, with its contents as its argument.
Re: Clojure macros continue to surprise me
#9Earlier quoted context omitted.
it can't be a function because the source is only guaranteed to be available at compile time, rather than at runtime.
A macro is a perfectly normal function. It's simply called at compile time, with its contents as its argument.
no you're misunderstanding me.
I'm saying that the macro's purpose is to read the source file and produce something at compile time. It's not a "normal" (read: runtime) function, as this feature cannot be implemented using a function that only executes at runtime.
Re: Clojure macros continue to surprise me
#10Earlier quoted context omitted.
A macro is a perfectly normal function. It's simply called at compile time, with its contents as its argument.
no you're misunderstanding me. I'm saying that the macro's purpose is to read the source file and produce something at compile time. It's not a "normal" (read: runtime) function, as this feature cannot be implemented using a function that only executes at runtime.
Sure, but the macro function is a normal function - it has inputs, outputs, and (preferably) should be pure. There's nothing special about the macro function itself, really.
You can see it explicitly in Common Lisp, where you can easily access and replace a macro-function with a custom one that you DEFUN yourself, like this.
CL-USER> (defun my-quote-fn (form env)
(declare (ignore env))
(destructuring-bind (operator &rest body) form
(assert (eq operator 'my-quote))
(list* 'quote body)))
MY-QUOTE-FN
CL-USER> (my-quote-fn '(my-quote (+ 2 2)) nil)
'(+ 2 2)
CL-USER> (setf (macro-function 'my-quote) #'my-quote-fn)
#
CL-USER> (macroexpand-1 '(my-quote (+ 2 2)))
'(+ 2 2)
T