on 14-Dec-2014 (Sun)

Tags

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

Question

How to express s.indexOf(’o’, 5) in operator notation?

Answer

s indexOf ('o', 5)

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

Question

Scala will transform the expression -2.0 into [...]

Answer

the method invocation (2.0).unary_-

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

Question

if you define a method unary_* and then try to call it on object in prefix notation *p, how will Scala parse it and why?

Answer

*.p because * is not one of the four names allowed for prefix methods

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

Question

Answer

take no arguments, when they are invoked without a dot and parentheses

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

Question

How does scala decide on precedence when methods are used in operator notation, like 2 + 2 * 7 ? What is Scala's default rule here?

Answer

Scala decides precedence based on the first character of the methods used in operator notation (this rule has exceptions). If the method name starts with a *, for example, it will have a higher precedence than a method that starts with a +.

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

Question

Why won't this compile?

class Rational(n: Int, d: Int) { // This won’t compile
  require(d != 0)
  override def toString = n +"/"+ d
  def add(that: Rational): Rational =
  new Rational(n * that.d + that.n * d, d * that.d)
}

Answer

Because n and d can only be accessed in methods for this object - they seem to be captured like in closure for toString. They are not fields / members though

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

Question

Answer

auxiliary constructors

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

Question

How to call Thread.yield() in Scala, where yield is a reserved word?

Answer

Thread.`yield`()
string enclosed in backticks becomes an identifier, no matter how arbitrary it is.

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

Question

How to write Unit as a literal?

Answer

()

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

Question

Why doesn't it work?

var line = ""
while ((line = readLine()) != "") // This doesn’t work!
  println("Read: "+ line)

Answer

the result of assignment expression is always Unit, so the above check Unit != "" is always true

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

Question

How to change it to exclude upper bound 4?

for (i <- 1 to 4)
  println("Iteration "+ i)

Answer

Use until method instead of to method:

for (i <- 1 until 4)
  println("Iteration "+ i)

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

Question

How to move the condition to the generator in the loop?

for (file <- filesHere)
  if (file.getName.endsWith(".scala"))
    println(file)

Answer

for (file <- filesHere if file.getName.endsWith(".scala"))
  println(file)

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

Question

What happens if you put multiple <- clauses in for?

Answer

You will get nested loops.

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

Question

How can you reduce number of semicolons in for loop?

Answer

Use curly braces instead of parentheses - Scala compiler will not infer semicolons in parentheses.

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

Question

How to introduce a val like variable mid-stream into for clauses?

Answer

Simply x=<whatever>, like val x=<whatever> elsewhere in the code, but without val keyword.

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

Question

What form of for produces a new collection?

Answer

for clauses yield body

Keyword yield makes body compute elements of the new collection.

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

Question

What will calling f() return?

def f(): Int = try { return 1 } finally { return 2 }

Answer

2

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

Question

What will calling g() return?

def g(): Int = try { 1 } finally { 2 }

Answer

1

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#asset-swap #finance #gale-using-and-tradning-asset-swaps

Question

Answer

bond dirty price at settlement.

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#asset-swap #finance #gale-using-and-tradning-asset-swaps

Question

Answer

par (of the bond)

Tags

#asset-swap #finance #gale-using-and-tradning-asset-swaps

Question

Answer

dirty price