Turn In Practice Scala #12
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…ce-scala Prof Ben updated tests for this assignment.
| */ | ||
| def totalPeopleInRooms(rooms: Map[Int, Option[String]]): Int = { | ||
| error("Fix me") | ||
| //rooms.keys.map(roomNumToOccupancy(rooms, _: Int)).foldLeft(0)(_ + _) |
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Oops, sorry I should have deleted this line before I submitted!
| * - the value can be: | ||
| * -- the amount of people in the room (filled: Some("10"), empty: None) | ||
| * -- the room is not available (Some("locked")) | ||
| */ |
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I fixed some >80 char lines. (gotta pass linecheck)
| def older(p: Person): Option[String] = { | ||
| error("fix me") | ||
| p match { | ||
| case Person(name, age) if age > 30 => Some(name) |
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I should have just used an if statement here, but I had just gotten addicted to case statements from the previous problem.
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| From reading the scala documentation intro, it became clear that support for | ||
| DSLs is a key feature, under the extensibility section. This can be seein in | ||
| the ability to customize the syntax for specific domains, the freedom of |
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I agree! This does facilitate the creation of DSLs :)
| preferred paradigm upon users. For example, the use of a functional style, | ||
| while well supported, is not the only way to write ones code. | ||
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| This was encouraging, especially comparing it to Haskell, which is very |
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I've never programmed in Haskell, but I have programmed in SML (which I hear is similar) and this is definitely the case. It made SML quite hard to learn at first.
| I think this was part of the testing suite rather than a Scala design | ||
| decision, but I really liked the way the testing suite reported how the | ||
| code result differed from an expected value. For example, we have | ||
| `"A person named[:] Jack" vs "A person named[] Jack"`, allowing us |
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Yes -- a good testing suite was so helpful!
| def expt(n: Int, e: Int): Int = -1 | ||
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| } | ||
| def expt(n: Int, e: Int): Int = { |
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another way to do this, when the exponent is an even #, is to do
if (e == 0) 1
else if (e%2) ((expt(n, e/2))* (expt(n, e/2)))
else n * expt(n, e - 1)
| } else if (room_state.get.get == "locked") { | ||
| "not available" | ||
| } else { | ||
| room_state.get.get |
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nice, I didn't think to use room_state.get.get
| case str : String => s"A string with length ${str.length()}" | ||
| case n : Int => "A positive integer" | ||
| case p : Person => s"A person with name: ${p.name}" | ||
| case seq @ Seq(_ *) if seq.length > 10 => "Seq with more than 10 elements" |
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I didn't think to use the @ symbol!
| */ | ||
| def sumOfList(l: List[Int]): Int = { | ||
| error("fix me") | ||
| l.foldLeft(0)(_ + _) |
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foldLeft was something I didn't figure out for a while, so good for you for figuring out how to use it :)
| * - ... etc | ||
| */ | ||
| def nthElementInList[T](n: Int, l: List[T]): T = { | ||
| error("fix me") |
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I tried to do something similar, but couldn't, so thank you for figuring it out! What I tried to do was to remove all the elements in indices 0 through n-1, and then returning the head of the remaining list.
| def elementExists[T](l: List[T], e: T): Boolean = { | ||
| error("fix me") | ||
| l match { | ||
| case List() => false |
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I really like how you did this. This is similar to what I tried, based on my limited knowledge of SML.
| error("fix me") | ||
| l match { | ||
| case List() => false | ||
| case x :: xs => (x == e) || elementExists(xs, e) |
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So once it finds the element (and returns true), it stops, correct? Otherwise it keeps looking for the element in the first index of the remainder of the list?
| def tails[T](l: List[T]): List[List[T]] = { | ||
| error("fix me") | ||
| l match { | ||
| case List() => List(l) |
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What's the difference between saying what you said in the first case and saying the following:
case List() => l
?
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Yay