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Flashcard 149629596

Tags

#odersky-programming-in-scala-2ed #scala

Question

What does to stand for in this example?


for (i <- 0 to 2)
  print(greetStrings(i))

Answer

a method call (0).to(2)
if a method takes only one parameter, you can call it without a dot or parentheses.

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Flashcard 149629623

Tags

#odersky-programming-in-scala-2ed #scala

Question

What does + really stand for in 2 + 3?

Answer

it is a method call: (2).+(3)
method is named "+"

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Flashcard 149629643

Tags

#odersky-programming-in-scala-2ed #scala

Question

if greetStrings is an array, greetStrings(i) gets transformed into

Answer

greetStrings.apply(i)

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Flashcard 149629682

Tags

#odersky-programming-in-scala-2ed #scala

Question

What will greetStrings(0) = "Hello" be transformed into?

Answer

greetStrings.update(0, "Hello")

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Flashcard 149629693

Tags

#odersky-programming-in-scala-2ed #scala

Question

What method are you calling here and where is it defined?
val numNames = Array("zero", "one", "two")

Answer

a factory method apply which takes variable number of argumetns and is defined on Array companion object
the code gets transformed to
val numNames2 = Array.apply("zero", "one", "two")

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Flashcard 149632156

Tags

#odersky-programming-in-scala-2ed #scala

Question

The order of mixins is significant.Roughly speaking, traits further to the [...]take effect first.

Answer

right

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The order of mixins is significant.Roughly speaking, traits further to the right take effect first.

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Flashcard 149632194

Tags

#odersky-programming-in-scala-2ed #scala

Question


class Animal
trait Furry extends Animal
trait HasLegs extends Animal
trait FourLegged extends HasLegs
class Cat extends Animal with Furry with FourLegged

The last part of the linearization of Cat is the linearization of its [...], which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but
all classes that are already in the linearization of Animal are left out now. This is preceded by the linearization of FourLegged, where again any classes
that have already been copied in the linearizations of the superclass or the first mixin are left out.

Answer

superclass, Animal

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#13; class Animal trait Furry extends Animal trait HasLegs extends Animal trait FourLegged extends HasLegs class Cat extends Animal with Furry with FourLegged The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but all classes that are already in the linearization of Animal are left out n

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Flashcard 149632201

Tags

#odersky-programming-in-scala-2ed #scala

Question


class Animal
trait Furry extends Animal
trait HasLegs extends Animal
trait FourLegged extends HasLegs
class Cat extends Animal with Furry with FourLegged

The last part of the linearization of Cat is the linearization of its superclass, Animal, which is [...]. The second to last part is the linearization of the first mixin, trait Furry, but
all classes that are already in the linearization of Animal are left out now. This is preceded by the linearization of FourLegged, where again any classes
that have already been copied in the linearizations of the superclass or the first mixin are left out.

Answer

copied as-is

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y extends Animal trait HasLegs extends Animal trait FourLegged extends HasLegs class Cat extends Animal with Furry with FourLegged The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but all classes that are already in the linearization of Animal are left out now. This is preceded by

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Flashcard 149632212

Tags

#odersky-programming-in-scala-2ed #scala

Question


class Animal
trait Furry extends Animal
trait HasLegs extends Animal
trait FourLegged extends HasLegs
class Cat extends Animal with Furry with FourLegged

The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the [...], but all classes that are already in the linearization of Animal are left out now. This is preceded by the linearization of FourLegged, where again any classes that have already been copied in the linearizations of the superclass or the first mixin are left out.

Answer

first mixin, trait Furry

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ends HasLegs class Cat extends Animal with Furry with FourLegged The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but all classes that are already in the linearization of Animal are left out now. This is preceded by the linearization of FourLegged, where again any classes that have already been co

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Flashcard 149632226

Tags

#odersky-programming-in-scala-2ed #scala

Question


class Animal
trait Furry extends Animal
trait HasLegs extends Animal
trait FourLegged extends HasLegs
class Cat extends Animal with Furry with FourLegged

The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but all classes that are [...]are left out now. This is preceded by the linearization of FourLegged, where again any classes that have already been copied in the linearizations of the superclass or the first mixin are left out.

Answer

already in the linearization of Animal

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th FourLegged The last part of the linearization of Cat is the linearization of its superclass, Animal, which is copied as-is. The second to last part is the linearization of the first mixin, trait Furry, but all classes that are already in the linearization of Animal are left out now. This is preceded by the linearization of FourLegged, where again any classes that have already been copied in the linearizations of the superclass or the first mixin ar

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Annotation 149632449

#scala

Methods in Scala are not values, but functions are.

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tpolecat
to when people get confused on #scala, but it turns out that there are a lot of cases to consider. It would be nice if this could just be the last word on methods vs. functions in Scala, so if I missed anything please let me know. TL;DR ... Methods in Scala are not values, but functions are. You can construct a function that delegates to a method via η-expansion (triggered by the trailing underscore thingy). The definition I will be using here is that a method is something

Annotation 149632456

#scala

You can construct a function that delegates to a method via η-expansion (triggered by the trailing underscore thingy).

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tpolecat
out that there are a lot of cases to consider. It would be nice if this could just be the last word on methods vs. functions in Scala, so if I missed anything please let me know. TL;DR ... Methods in Scala are not values, but functions are. You can construct a function that delegates to a method via η-expansion (triggered by the trailing underscore thingy). The definition I will be using here is that a method is something defined with def and a value is something you can assign to a val. The Basic Idea When we define a method we see that

Annotation 149632463

#scala

by adding the η-expansion postfix operator (η is pronounced "eta"), we can turn the method into a function value.

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tpolecat
with `_' if you want to treat it as a partially applied function val f = add1 ^ Note also the type of add1, which doesn't look normal; you can't declare a variable of type (n: Int)Int. Methods are not values. However, by adding the η-expansion postfix operator (η is pronounced "eta"), we can turn the method into a function value. Note the type of f. scala> val f = add1 _ f: Int => Int = scala> f(3) res0: Int = 4 The effect of _ is to perform the equivalent of the following: we construct a Function1 in

Annotation 149632470

#scala

The effect of _ is to perform the equivalent of the following: we construct a Function1 instance that delegates to our method.

scala> val g = new Function1[Int, Int] { def apply(n: Int): Int = add1(n) }
g: Int => Int = <function1>

scala> g(3)
res18: Int = 4

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tpolecat

Annotation 149632487

#scala

The return keyword is not "optional" or "inferred"; it changes the meaning of your program, and you should never use it.

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tpolecat
May 09, 2014 Don't Use Return in Scala Alright, every time Martin's Coursera course runs we get people in #scala asking why they get style points taken off for using return. So here's the pro tip: The return keyword is not "optional" or "inferred"; it changes the meaning of your program, and you should never use it. Let's look at a little example. // Add two ints, and use this method to sum a list def add(n:Int, m:Int): Int = n + m def sum(ns: Int*): Int = ns.foldLeft(0)(add) scala> sum(33, 42,

Annotation 149632494

#scala

// Inline add and addR
def sum(ns: Int*): Int = ns.foldLeft(0)((n, m) => n + m) // inlined add

scala> sum(33, 42, 99)
res2: Int = 174 // alright

def sumR(ns: Int*): Int = ns.foldLeft(0)((n, m) => return n + m) // inlined addR

scala> sumR(33, 42, 99)
res3: Int = 33 // um.

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tpolecat
(addR) scala> sumR(33, 42, 99) res1: Int = 174 So far so good. There is no apparent difference between sum and sumR which may lead you to think that return is simply an optional keyword. But let's refactor a bit by inlining add and addR. // Inline add and addR def sum(ns: Int*): Int = ns.foldLeft(0)((n, m) => n + m) // inlined add scala> sum(33, 42, 99) res2: Int = 174 // alright def sumR(ns: Int*): Int = ns.foldLeft(0)((n, m) => return n + m) // inlined addR scala> sumR(33, 42, 99) res3: Int = 33 // um. What the what? So, the short version is: A return expression, when evaluated, abandons the current computation and returns to the caller of the method in which return appears. So in

Flashcard 149632499

Tags

#scala

Question

// Inline add and addR
def sum(ns: Int*): Int = ns.foldLeft(0)((n, m) => n + m) // inlined add

scala> sum(33, 42, 99)
res2: Int = 174 // alright

def sumR(ns: Int*): Int = ns.foldLeft(0)((n, m) => return n + m) // inlined addR

scala> sumR(33, 42, 99)
res3: ???

What will this expression return and why?

Answer

33 // um.

A return expression, when evaluated, abandons the current computation and returns to the caller of the method in which return appears.

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Int*): Int = ns.foldLeft(0)((n, m) => n + m) // inlined add scala> sum(33, 42, 99) res2: Int = 174 // alright def sumR(ns: Int*): Int = ns.foldLeft(0)((n, m) => return n + m) // inlined addR scala> sumR(33, 42, 99) res3: Int = 33 // um. <body><html>

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on 07-Sep-2014 (Sun)

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