[plt-scheme] How to apply a multi-argument function to each element of a list
My mistake, you are using Pretty Big.
To the below suggestions, add:
(require scheme/function)
...to the top of any file using the "curry" function.
Carl Eastlund
On Tue, Mar 2, 2010 at 6:59 PM, Carl Eastlund <carl.eastlund at gmail.com> wrote:
> Barry,
>
> There are a few options.
>
> You can have the students write:
>
> (define (encrypt-message m)
> (encrypt 17 40 m))
>
> Then you dodge this problem entirely.
>
> Or you can write:
>
> (map (curry encrypt 17 40) (list ...))
>
> Be careful with the "curry" function. It can do funny things if the
> function you give it accepts a variable number of arguments. But for
> a simple 3-argument function like "encrypt", it should work just fine.
>
> Or you can write any number of variations on your own version of
> "curry" and give it to students. But you probably want the above, to
> keep things simple.
>
> Carl Eastlund
>
> On Tue, Mar 2, 2010 at 6:54 PM, Barry Brown <barry at cs.sierracollege.edu> wrote:
>> Sorry this is probably a basic question. Other than being familiar with the
>> HtDP material, I am kind of a Scheme newbie.
>>
>> I'm working on an assignment for my students to implement RSA encryption.
>> One of the problems is, naturally, to write a function called encrypt that
>> consumes the encryption key pair e and n, along with a message m to encrypt.
>> They are using the Pretty Big language.
>>
>> encrypt : number number number -> number
>>
>> I would then like to use the encrypt function to encrypt a list of numbers.
>> Now, if Scheme had implicit currying like Haskell, I could do something like
>> this:
>>
>> (map (encrypt 17 40) (list 100 115 76))
>>
>> How can I do this in Scheme? The students have not seen lambda, nor will
>> they be introduced to it. This for a course in discrete structures; I'm
>> using Scheme to help illustrate some of the concepts they are learning.
>>
>> I think the syntax ought to be similar to the "apply" function, but instead
>> of constructing an argument list, it applies the function to each element of
>> the list, using the two given arguments:
>>
>> (apply-func encrypt 17 40 (list 100 115 76))
>>
>> would be equivalent to:
>>
>> (list (encrypt 17 40 100) (encrypt 17 40 115) (encrypt 17 40 76))
>>
>> Thanks in advance!
>>
>> -B
>