This seems like a good use for a macro. A couple of thoughts:
1. Use arrays instead of lists
In clojure, it is "best practice" to use arrays for data. So, your
macro call should look like this.
(match [1 2 3]
[1 x] (+ x x)
[1 x y] (+ x y))
2. Could you post the source to match maker? That would help my play
around in a REPL
3. As for books go, get yourself a copy of "Programming Clojure" by
Stuart Holloway
Sean
On Jul 8, 11:42 am, Jonas <jonas.enl...@gmail.com> wrote:
> Hi.
>
> I'm developing a simple pattern matching library for clojure but I am
> having
> trouble with macros (which I have almost zero experience with).
>
> I have a function `make-matcher`
>
> (make-matcher <pattern>)
>
> which returns a function that can pattern match on data and returns a
> map of bindings (or nil in case of a non-match).
>
> ((make-matcher '(list x y z w)) (list 1 2 3 4))
> ; => {x 1 y 2 z 3 w 4}
> ((make-matcher '(list x y z x)) (list 1 2 3 4))
> ; => nil
> ((make-matcher '(list 1 x 2 _)) (list 1 2 3 4))
> ; => nil
> ((make-matcher '(list 1 x 2 _)) (list 1 3 2 9))
> ; => {x 3}
>
> I have been trying to write the following 'match' macro:
>
> (match <data>
> <pattern-1> <body-1>
> <pattern-2> <body-2>)
>
> The macro should work like this:
>
> (match (list 1 2 3)
> (list 1 x) (+ x x)
> (list 1 x y) (+ x y))
> ; => 5
>
> I have the following macros (none of which works correctly):
>
> ; (letmap {a 1 b 2} (+ a b))
> ; =(should) expand to=>
> ; (let [a 1 b 2] (+ a b))
> (defmacro letmap [dict & body]
> `(let ~(into [] (reduce concat (eval dict)))
> (do ~...@body)))
>
> ; (match (list 1 2 3)
> ; (list 1 x) (+ x x)
> ; (list 1 x y) (+ x y))
> ; =should expand to something like=>
> ; (let [dict (<matcher..> (list 1 2 3))]
> ; (if dict
> ; (letmap dict (+ 1 x))
> ; (match (list 1 2 3) (list 1 x y) (+ x y))))
> (defmacro match [data & clauses]
> (when clauses
> (let [pattern (first clauses)
> body (second clauses)
> matcher (make-matcher pattern)]
> `(let [dict# (~matcher ~data)]
> (if dict#
> (letmap dict# ~body)
> (match ~data (next (next ~clauses))))))))
>
> Any help is appreciated. Also pointers to documents and books where I
> can
> learn more about macros.
>
> Thanks.
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