Purpose of this assignment

• Provide a basic understanding of macros.

General idea of the assignment

A macro definition is very similar to a function definition. However, when a function is called, it returns a value; when a macro is called, it returns code, which is then executed. Macros let you "extend the language," and are widely considered (by Lisp enthusiasts) to be what makes Lisp so great.

Details

• The name of a function, such as pos? -- in this case, the test should apply the function to the value, as (pos? value).
• You can test if f is a function with (function? f), but first you have to (ns user (:use clojure.test)).
• A nonempty list whose first element is a function, such as (> 0) -- in this case, the value should be inserted as the second element,  as (> value 0).
• If some other value -- in this case, the test is whether the two values are equal.
• The keyword :else, which in a cond is equivalent to true.

    (match v
        7     "lucky number"
        pos?  "positive"
        (< 0) "negative"
        :else "zero" )

    (cond
        (= v 7)  "lucky number"
        (pos? v) "positive"
        (< v 0)  "negative"
        :else    "zero" )

Suggested reading

• Clojure from the ground up: macros
• Clojure macros for beginners
• Writing Macros: Clojure for the Brave and True
• List comprehensions in eight lines of Clojure (advanced!)

What to turn in

Turn in

• A Clojure program inplementing your match macro, and using it in two or three examples.
• A file named readme.txt, describing how to use your macro, and giving an example use and an example macro expansion.

Due date