Well, this all looks very familiar. Can I ask where this course is offered?
Okay, let's start with part of the problem definition:
> Create a function that calculates the number of days in a month given a year
> and a month
>
> Call the function number-of-days-in-month, and it's signature is number,
> number -> number
Let's put these two statements together. In fact, let's start with the
second one, specifically: "[the function's] signature is number,
number -> number." That means the function takes two arguments, both
of which are numbers, and it returns a number. That's not very
informative. If that were all the information you had, you might start
your function definition like this:
(define (number-of-days-in-month one-number a-second-number)
[ somehow calculate yet a third number ])
But the previous sentence gives you more information. It says, "[the
function] calculates the number of days in a month given a year and a
month." This is a actually a more specific version of what the
signature tells you. Let me reverse the order of the statement to make
this more clear: "Given a year and a month, the function calculates
the number of days in the month."
So the "numbers" in the signature aren't any old numbers. Let's look
at the signature again:
number, number -> number
The things to the left of the arrow are what the function is given.
The problem says that the function is given a year and a month. So
let's restate the signature, adding that information:
year-number, month-number -> number
The thing to the right of the arrow is what the function calculates,
in this case the number of days in the given month. (This is where
things get a little complicated. You're trying to calculate the number
of days in the month that you're given. Fine, so why are you given a
year in addition to the month? The answer to this question will help
you when you start to fill in your function body. By the way, I'm not
trying to be patronizing. I'm pretty sure you know the answer to this
question, given what you wrote in your message. But it may help to
think about it this way.) So let's add this information to the
signature:
year-number, month-number -> number-of-days-in-month
Or, in English: "`number-of-days-in-month` is a function that takes a
year number and a month number and returns the number of days in the
month." If you're skeptical of my claim that this is more specific
than the signature we started with, consider that not all numbers are
valid year-numbers or month-numbers. For example, 2.5 isn't the number
of a year (well, not in the Gregorian calendar, anyhow), and -20 isn't
the number of a month.
So now at least, we should be able to replace the "??"s in your
function skeleton:
(define (number-days-in-month year-number month-number)
(cond
[
As for the conditional in the function body, go back to the question I
posed above: why are you given a year-number in addition to a
month-number if you're just supposed to find the number of days in a
month?
- Jon
On Sun, Apr 19, 2020 at 2:50 PM Suz Renae <kahrend...@gmail.com> wrote:
>
> I am new to racket (first year student) and since class has been pushed to
> online only, I am having a harder time.
>
> We are currently working on vectors and hash tables. I feel like I keep
> overthinking it and keep getting stuck. I know that the first parameter in
> the function will be the year and the second will be the (vector-ref months
> x)that I pull from the defined vector.
>
> The question I am having a hard time with and what I have actually done below.
>
> Create a function that calculates the number of days in a month given a year
> and a month
>
> Call the function number-of-days-in-month, and it's signature is number,
> number -> number
> Example:
> (number-days-in-month 2016 1) -> 31
> (number-days-in-month 2016 11) -> 30
> (number-days-in-month 2016 12) -> 31
> (number-days-in-month 1900 2) -> 28
> (number-days-in-month 2000 2) -> 29
> (number-days-in-month 2016 2) -> 29
> (number-days-in-month 2200 2) -> 28
>
> What I have so far...
>
> ;Leap Year
> (define (leap-year? year)
> (and (zero? (modulo year 4))
> (or (not (zero? (modulo year 100)))
> (zero? (modulo year 400))
> )
> )
> )
>
> ;Months with days vector, beginning at an index of 0 since there is not 0th
> month
> (define months (vector 0 31 28 31 30 31 30 31 31 30 31 30 31))
>
> (check-expect(number-days-in-month 2016 1)31)
> (check-expect(number-days-in-month 2016 11)30)
> (check-expect(number-days-in-month 2016 12)31)
> (check-expect(number-days-in-month 1900 2)28)
> (check-expect(number-days-in-month 2000 2)29)
> (check-expect(number-days-in-month 2016 2)29)
> (check-expect(number-days-in-month 2200 2)28)
>
> I need help with building the actual function and what conditionals I should
> be using.
>
> (define (number-days-in month ?? ??)
> (cond
> [
>
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