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12. SCALA – CLOSURES Scala A closure is a function, whose return value depends on the value of one or more variables declared outside this function. The following piece of code with anonymous function. val multiplier = (i:Int) => i * 10 Here the only variable used in the function body, i * 10, is i, which is defined as a parameter to the function. Try the following code: val multiplier = (i:Int) => i * factor There are two free variables in multiplier: i and factor. One of them, i, is a formal parameter to the function. Hence, it is bound to a new value each time multiplier is called. However, factor is not a formal parameter, then what is this? Let us add one more line of code. var factor = 3 val multiplier = (i:Int) => i * factor Now factor has a reference to a variable outside the function but in the enclosing scope. The function references factor and reads its current value each time. If a function has no external references, then it is trivially closed over itself. No external context is required. Try the following example program. object Demo { } def main(args: Array[String]) { } println( "multiplier(1) value = " + multiplier(1) ) println( "multiplier(2) value = " + multiplier(2) ) var factor = 3 val multiplier = (i:Int) => i * factor Save the above program in Demo.scala. The following commands are used to compile and execute this program. 86
Scala \>scalac Demo.scala \>scala Demo Output: multiplier(1) value = 3 multiplier(2) value = 6 87
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Scala About the Tutorial Scala is a
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Scala 4. SCALA - DATA .............
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Scala Higher-Order Functions ......
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Scala Regular-Expression Examples .
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Scala Scala can Execute Java Code S
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Scala We assume that the readers of
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Scala Windows \>scala -version Scal
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Scala Welcome to Scala version 2.9.
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Scala $salary, 123abc, -salary Oper
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Scala Newline Characters Scala is a
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4. SCALA - DATA Scala Scala has all
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Scala "Hello,\nWorld!" "This string
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5. SCALA - VARIABLES Scala Variable
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Scala } Save the above program in D
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Methods Variables 6. SCALA - CLASSE
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Scala \>scala Demo Output Point x l
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Scala Implicit classes may not be
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7. SCALA - ACCESS MODIFIERS Scala T
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Scala } Scope of Protection Access
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8. SCALA - OPERATORS Scala An opera
Page 44 and 45: Scala == (Equal) 1 Checks if the va
Page 46 and 47: Scala It is called Logical AND oper
Page 48 and 49: Scala Ex: (A & B) will give 12, whi
Page 50 and 51: Scala \>scala Demo Output: a & b =
Page 52 and 53: Scala Try the following example pro
Page 54 and 55: Scala c &= a = 0 c ^= a = 10 c |= a
Page 56 and 57: 9. SCALA - IF ELSE STATEMENT Scala
Page 58 and 59: Scala if(Boolean_expression){ //Exe
Page 60 and 61: Scala }else if( x == 30 ){ println(
Page 62 and 63: 10. SCALA - LOOP STATEMENTS Scala T
Page 64 and 65: Scala while(condition) { Conditiona
Page 66 and 67: Scala jumps back up to do, and the
Page 68 and 69: Scala object Demo { } def main(args
Page 70 and 71: Scala } } Save the above program in
Page 72 and 73: Scala Scala's for loop allows to fi
Page 74 and 75: Scala \>scalac Demo.scala \>scala D
Page 76 and 77: Scala object Demo { def main(args:
Page 78 and 79: Scala Output: Value of a: 1 Value o
Page 80 and 81: 11. SCALA - FUNCTIONS Scala A funct
Page 82 and 83: Scala var sum:Int = 0 sum = a + b r
Page 84 and 85: Scala println("Arg value[" + i + "]
Page 86 and 87: Scala } Save the above program in D
Page 88 and 89: Scala logWithDateBound("message3" )
Page 90 and 91: Scala \>scala Demo Output Factorial
Page 92 and 93: Scala Currying Functions Currying t
Page 96 and 97: 13. SCALA - STRINGS Scala This chap
Page 98 and 99: Scala "My name is ".concat("Zara");
Page 100 and 101: Scala val name = “James” printl
Page 102 and 103: Scala b String Methods Following is
Page 104 and 105: Scala 27 28 29 30 31 32 33 34 35 36
Page 106 and 107: 14. SCALA - ARRAYS Scala Scala prov
Page 108 and 109: Scala } println("Total is " + total
Page 110 and 111: Scala Save the above program in Dem
Page 112 and 113: Scala print( " " + x ) } println()
Page 114 and 115: 15. SCALA - COLLECTIONS Scala Scala
Page 116 and 117: Scala val nums = Nil println( "Head
Page 120 and 121: Scala 1 2 3 4 5 6 7 8 9 10 11 12 13
Page 122 and 123: Scala 34 35 36 37 38 39 40 41 42 43
Page 126 and 127: Scala Find Common Values Insets You
Page 128 and 129: Scala 14 def diff(that: Set[A]): Se
Page 130 and 131: Scala 39 def sum: A Returns the sum
Page 132 and 133: Scala val nums: Map[Int, Int] = Map
Page 134 and 135: Scala colors.keys.foreach{ i => pri
Page 136 and 137: Scala 5 def iterator: Iterator[(A,
Page 138 and 139: Scala 30 def min: (A, B) Finds the
Page 140 and 141: Scala You can use Tuple to write a
Page 142 and 143: Scala Concatenated String: (1,hello
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Scala } } Save the above program in
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Scala 2 def isEmpty: Boolean Return
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Scala number of words Find Min & Ma
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Scala 4 def ++[B >: A](that :=> Gen
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Scala 28 def max: A Finds the large
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16. SCALA - TRAITS Scala A trait en
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Scala Value classes and Universal T
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17. SCALA - PATTERN MATCHING Scala
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Scala val charlie = new Person("Cha
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18. SCALA - REGULAR EXPRESSIONNS Sc
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Scala \\n Back-reference to capture
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Scala val pattern = new Regex("abl[
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Scala } } } } Save the above progra
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20. SCALA - EXTRACTORS Scala An ext
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Scala def main(args: Array[String])
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Scala print("Please enter your inpu
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