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Previously on Pixel Shaker : an image is a bounded function that can be coded as a Java-class. This Java-class involves a lots codelines, even in Clojure. Today is an exploration of this concept in a more idiomatic way.

A bounded function is a function with an additional information : its definition domain. Clojure provides an handy way to deals with extra data : the metadata. The metadata is a map of data that can be added using the with-meta function. Let’s try to add a definition domain as a metadata :

user> (defn indom? [dom pt]
        (let [[start end] dom
              [x y] pt]
          (and (>= x (first start))
               (<= x (first end))
               (>= y (second start))
               (<= y (second end)))))
#'user/indom?
user> (defn f [x y] (+ x y))
#'user/f
user> (def dom [[0 0] [4 4]])
#'user/dom
user> (def bf (with-meta f {:domain dom}))
java.lang.UnsupportedOperationException (NO_SOURCE_FILE:10)

(more…)

Tags: clojure, image, programmation, représentation