scala-exercises / exercises-scalatutorial

Exercises for the "Functional Programming Principles in Scala", part of the FP in Scala specialized program by EPFL.

Scala Exercises - Functional Programming Principles library

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This repository hosts a library for the first course of the Scala MOOC ("Functional Programming Principles in Scala").

Run Locally

• Clone this repository, compile and publish the project:

git clone [email protected]:scala-exercises/exercises-scalatutorial.git
cd exercises-scalatutorial/
sbt compile publishLocal # it is important to first run the `compile` command alone

• Clone the evaluator and run it:

git clone [email protected]:scala-exercises/evaluator.git
cd evaluator/
sbt "project evaluator-server" run

• Clone the scala-tutorial branch of our scala-exercises fork:

git clone -b scala-tutorial [email protected]:scalacenter/scala-exercises.git

• Follow the database setup instructions given here

• Add the following line the server/conf/application.dev.conf:

evaluator.secretKey="secretKey"

• Run the server:

sbt -mem 1500 run

About Scala exercises

"Scala Exercises" brings exercises for the Stdlib, Cats, Shapeless and many other great libraries for Scala to your browser. Offering hundreds of solvable exercises organized into several categories covering the basics of the Scala language and it's most important libraries.

Scala Exercises is available at scala-exercises.org.

Contributing

Contributions welcome! Please join our Gitter channel to get involved, or visit our GitHub site.

License

Copyright (C) 2015-2016 47 Degrees, LLC. Reactive, scalable software solutions. http://47deg.com [email protected]

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

exercises-scalatutorial's Issues

Apparent Error in Higher Order Functions section

https://github.com/scala-exercises/exercises-scalatutorial/blob/master/src/main/scala/scalatutorial/sections/HigherOrderFunctions.scala#L126-L138

If I try to run code like this, I get:

Welcome to Scala 2.12.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_162-ea).
Type in expressions for evaluation. Or try :help.

scala> { def f(x1: Int, x2: Int) = x1 + x2 ; f }
<console>:12: error: missing argument list for method f
Unapplied methods are only converted to functions when a function type is expected.
You can make this conversion explicit by writing `f _` or `f(_,_)` instead of `f`.
       { def f(x1: Int, x2: Int) = x1 + x2 ; f }
                                             ^

scala> 

list exercise error

According to https://github.com/scala-exercises/exercises-scalatutorial/blob/master/src/main/scala/scalatutorial/sections/StandardLibrary.scala#L72-L97

val nums = Nil.::(4).::(3).::(2).::(1)

nums match {
  // Lists of `Int` that starts with `1` and then `2`
  case 1 :: 2 :: xs => …
  // Lists of length 1
  case x :: Nil => …
  // Same as `x :: Nil`
  case List(x) => …
  // The empty list, same as `Nil`
  case List() =>
  // A list that contains as only element another list that starts with `2`
  case List(2 :: xs) => …
}

the last case of case List(2 :: xs) gives error because the inferred type is List[Int] but the case signature is expecting List[List[Int]]. Please correct me if I am wrong. If I am not then how should it be re-written?

type mismatch with example

Hi,

I am following this tutorial. Awesome work. However, I couldn't get this example working with the code provided.

trait Stream[+T] {
    def prepend[U >: T](elem: U) : Stream[U] = Stream.cons(elem, this)
}

Compiling the code above gives me error as following.

polymorphism.scala:15: error: type mismatch;
 found   : Stream[T]
 required: scala.collection.immutable.Stream[?]
           def prepend[U >: T](elem: U) : Stream[U] = Stream.cons(elem, this)

Did I miss something?

exercises-scalatutorial/src/main/scala/scalatutorial/sections/PolymorphicTypes.scala

Line 433 in 38531b1

* def prepend [U >: T](elem: U): Stream[U] = Stream.cons(elem, this)

Rename `aux` folder in `exercises-scalatutorial` content library, as its incompatible in Windows machines

ERROR -> object aux is not a member of package scalatutorial at [186, 186, 186]

Answer to Dynamic Binding part of Object Oriented Programming should be false followed by true as its asserted but there is the exception instead
https://github.com/scala-exercises/exercises-scalatutorial/search?utf8=%E2%9C%93&q=dynamicBinding

org.scalaexercises.definitions.Section

org.scalaexercises.definitions.Section is not found while importing it.

Adds org sbt settings and integrates with Travis

Align the library settings with the rest of the exercises libraries within scala-exercises.org.

• Common sbt-settings
• Add to https://travis-ci.org/scala-exercises
• Publish to Sonatype, within the scala-exercises organization

Random Test Failure

It seems like with latest merge now we have random test failures related to check rational ordering.

https://travis-ci.org/scala-exercises/exercises-scalatutorial/builds/216055586

Most of the times it's happening here:

https://github.com/scala-exercises/exercises-scalatutorial/blob/master/src/test/scala/scalatutorial/sections/TypeClassesSpec.scala#L18-L22

Evaluation failed : Compilation Error ; ERROR -> object aux is not a member of package scalatutorial at [186, 186, 186]

In page https://www.scala-exercises.org/scala_tutorial/object_oriented_programming: both exercises will show Evaluation failed : Compilation Error ; ERROR -> object aux is not a member of package scalatutorial at [186, 186, 186] after clicking run.

Factorial function seems to not work

I can't refer the variable result that's definitely in scope for the function for some reason.

Also, Looking at the source code, the code is actually different than the one shown here.

Unexpected value in Lazy Evaluation exercise

Dear Team,

One of the exercises in Lazy Evaluation section returns odd result:

Same function in tests:

class LazyEvaluationSpec extends RefSpec with Checkers {

  def `check lazy list range`(): Unit =
    check(Test.testSuccess(LazyEvaluation.llRangeExercise _, 3 :: HNil)

Scala Tutorial: the last exercise of Lazy Evaluation, builder.result() shouldBe "xyzz"

ran it on scala 2.10.7 and the result is "xyzz", but this answer cannot pass, is something wrong?

I can't press run button

When i try to solve the exercise, i can't press run button, neither in the mobile browser nor in the computer browser.

That could be happening?

Syntax isn't introduced

There's no point where the following syntax is introduced:

exercises-scalatutorial/src/main/scala/scalatutorial/sections/StandardLibrary.scala

Line 120 in 23b132f

val cond: (Int, Int) => Boolean = res0

Even trying to scour the internet, it's difficult to find the solution that's expected.

Exercises with nothing to fill in / impossible to complete

There are 3 "exercises" with nothing to fill in that can't be run or be marked as completed (so the corresponding sections can't also be counted as completed). The affected sections are:

• Structuring information: The exercise on Exhaustivity
• Classes Vs Case Classes: Empty exercise at the end of the section
• Lazy Evaluation: Empty exercise at the end of the section

Hope this helps and thanks for all the nice exercises!