Big Data series Cultivation-scala Course 06

about regular expressions in Scala in conjunction with pattern matching reg

The implementation of regular expressions: Regular expressions are defined in the same way as other languages, simply by adding an. R to the expression, and you can iterate through the corresponding expression to match

 //  regular expression defined  val regex= "" "([0-9]+) ( [a-z]+] "". R //  A constant of numbers and letters  Val Numpattern = "[0-9]+". R //  constant with numbers  Val Numberpattern = "" "\s+[0-9]+\s+" "". R //  by S and number +    The regular expression composed of S   println (regex);  //  Findallin method returns an iterator that iterates through all occurrences  Span style= "color: #0000ff;" >for  (matchstring <-numpattern.findallin ("99345 Scala, 22298 Spark" ))    println (matchstring)  //  Find first match  println (Numberpattern.findfirstin ("99ss Java, 222 Hadoop")) 

Reg implementations combined with pattern matching: Regular expressions may often be used in the future to combine pattern-matching

// Regular Expressions Combined    with pattern matching // Regular Expressions    // prescribed mode    Val line = "93459 spark" line    match{      case numitempattern (num, blog) = println (num + " \ t "+ Blog      " case _ = = println ("Oops ...")    } 

native functions and class-a civic functions in Scala

Local function Implementation: The function is included, which makes the function more secure.

  // a local function is a function that contains a function so that the inside function can use the arguments of the outside function def processdata (filename:string, Width:int) {    def processline (line:string) {      if ( Line.length > width)        + ":" + line )    }    = source.fromfile (filename)      for (Line <- source.getlines)      processline (line)  } }

Implemented as a class-a citizen function; enables more convenient use of function representations in the process

  //Class Citizen functiondef main (args:array[string]): Unit = {     //parameters set in the startup itemVal width = args (0). ToInt for(Arg <-args.drop (1) ) ProcessData (arg, width) var increase= (X:int) + x + 1println (Increase (10)) Increase= (X:int) + x + 9999Val somenumbers= List (-11,-10,-5, 0, 5, 10)      //iterating through an arraySomenumbers.foreach ((x:int) =print (x)) println//filter greater than 0Somenumbers.filter ((X:int) = x > 0). foreach ((x:int) =print (x)) println//filter greater than 0Somenumbers.filter ((x) = x > 0). foreach ((x:int) =print (x)) println//filter greater than 0Somenumbers.filter (x = x > 0). foreach ((x:int) =print (x)) println//filter greater than 0Somenumbers.filter (_ > 0). foreach ((x:int) =print (x)) println//define two numbers to addVal F = (_: Int) +(_: Int) println (f (5, 10))   }

How to explain the partial function in Scala

Partial function Implementation: Partial function can make the expression more concise, there is no need to write extra parameters

Partial function parsing: When the partial function is implemented, the Apply function is generated to perform the corresponding operation

 val data = List (1, 2, 3, 4, 5, 6)  //   Data.foreach (println _) Data.foreach (x  => PR INTLN (x)) def sum (A:int, B:int, c:int)  = a + b + C println (sum ( 1, 2, 3 = sum _  //  call define the SUM function directly, invoke its corresponding apply function  println (fp_a (1, 2, 3)) println (Fp_a.apply ( 1, 2, 3)) val fp_b  = SUM (1, _: Int, 3) println (Fp_b ( 2 10)) d Ata.foreach (println _) Data.foreach (println)  

about closures in Scala

Scala closure parsing: Let the function body implement redundant things with simple expressions

Scala Closure implementation

    def main (args:array[string]) {            = List (1, 2, 3, 4, 5, 6)    = 0    + = _)    = (X:int) + x +    more = Add (1)    = Add (9999)    println (A (  ))        println (b (10)

Scala's functional programming is really profound, a lot of things have been achieved by his bottom, which allows us to be more concise in the use of the process. We'll be here today.

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Big Data series Cultivation-scala Course 06