Calihan

I'm trying to write a really small program in scheme (lisp) that uses procedural abstraction, here is an example:

(define (make-exponent x)
(lambda (x)
(expt x n)))

(define square (make-exponent 2))

(square 2) ---> 4
(square 6) ---> 36

(define cube (make-expt 3))

(cube 3) ---> 9


You can see how this works.

Anyway I am supposed to write a function (calling it fmap) that takes as its arguments, a function f and a list l, and returns a list containing the results of f applied to l. Seems easy enough, but I just can't do it. I can see how the above example works but it's just not clicking for me. Does anyone even know scheme? lol =)

Calihan

Edit: Well the post took out what little formatting i gave it, and i obviously cant multiply because I had 3^3 = 9...

And apparently i don't know how to use the edit button. . .As I made a second post -_-

serge2k

use [code][/code] and you can save the formatting problem.

I'm diong scheme now actually.

is there any restrictions on what the function can be?

is it supposed to be like this

function (x y z) => (function(x) function(y) function(z))

or can you do something like this
+ (x y z) => x+y+z

?

Calihan

I don't know why I was having trouble with this. That's the working code right there. Please note that this function assumes that the function you are going to use only takes 1 parameter (list, atom, etc.) If you tried to use, let's say eq? with it, you wouldn't be able to pass in 2 things to compare. And also I just threw in that check for the null list as it was something related to my assignment that I didn't include last time.

Thats if you wanted to use eq?, as it will let you pass in 2 parameters. I'm sorry that I was a little confusing in my original post.

This would return a #f, like we assume it should.

And now as this was the first part of my assignment, I have to go back and rewrite some previous functions to use this fmap instead of the cars/cdrs/etc. they currently use. I assume all I have to do is pass that code into fmap instead of using it in my original. . .