Scala example source code file (interpreter.check)

This example Scala source code file (interpreter.check) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

any, any, array, array, bar, exp, exp, fact, foo, int, int, s, term, test

The Scala interpreter.check source code

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scala> 

scala> // basics

scala> 3+4
res0: Int = 7

scala> def gcd(x: Int, y: Int): Int = {
          if (x == 0) y
          else if (y == 0) x
          else gcd(y%x, x)
}
gcd: (x: Int, y: Int)Int

scala> val five = gcd(15,35)
five: Int = 5

scala> var x = 1
x: Int = 1

scala> x = 2
x: Int = 2

scala> val three = x+1
three: Int = 3

scala> type anotherint = Int
defined type alias anotherint

scala> val four: anotherint = 4
four: anotherint = 4

scala> val bogus: anotherint = "hello"
<console>:8: error: type mismatch;
 found   : java.lang.String("hello")
 required: anotherint
       val bogus: anotherint = "hello"
                               ^

scala> trait PointlessTrait
defined trait PointlessTrait

scala> val (x,y) = (2,3)
x: Int = 2
y: Int = 3

scala> println("hello")
hello

scala> 

scala> // ticket #1513

scala> val t1513 = Array(null)
t1513: Array[Null] = Array(null)

scala> // ambiguous toString problem from #547

scala> val atom = new scala.xml.Atom()
atom: scala.xml.Atom[Unit] = ()

scala> // overriding toString problem from #1404

scala> class S(override val toString : String)
defined class S

scala> val fish = new S("fish")
fish: S = fish

scala> // Test that arrays pretty print nicely.

scala> val arr = Array("What's", "up", "doc?") 
arr: Array[java.lang.String] = Array(What's, up, doc?)

scala> // Test that arrays pretty print nicely, even when we give them type Any

scala> val arrInt : Any = Array(1,2,3)
arrInt: Any = Array(1, 2, 3)

scala> // Test that nested arrays are pretty-printed correctly

scala> val arrArrInt : Any = Array(Array(1, 2), Array(3, 4))
arrArrInt: Any = Array(Array(1, 2), Array(3, 4))

scala> 

scala> // implicit conversions

scala> case class Foo(n: Int)
defined class Foo

scala> case class Bar(n: Int)
defined class Bar

scala> implicit def foo2bar(foo: Foo) = Bar(foo.n)
foo2bar: (foo: Foo)Bar

scala> val bar: Bar = Foo(3)
bar: Bar = Bar(3)

scala> 

scala> // importing from a previous result

scala> import bar._
import bar._

scala> val m = n
m: Int = 3

scala> 

scala> // stressing the imports mechanism

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> val one = 1
one: Int = 1

scala> 

scala> 

scala> val x1 = 1
x1: Int = 1

scala> val x2 = 1
x2: Int = 1

scala> val x3 = 1
x3: Int = 1

scala> val x4 = 1
x4: Int = 1

scala> val x5 = 1
x5: Int = 1

scala> val x6 = 1
x6: Int = 1

scala> val x7 = 1
x7: Int = 1

scala> val x8 = 1
x8: Int = 1

scala> val x9 = 1
x9: Int = 1

scala> val x10 = 1
x10: Int = 1

scala> val x11 = 1
x11: Int = 1

scala> val x12 = 1
x12: Int = 1

scala> val x13 = 1
x13: Int = 1

scala> val x14 = 1
x14: Int = 1

scala> val x15 = 1
x15: Int = 1

scala> val x16 = 1
x16: Int = 1

scala> val x17 = 1
x17: Int = 1

scala> val x18 = 1
x18: Int = 1

scala> val x19 = 1
x19: Int = 1

scala> val x20 = 1
x20: Int = 1

scala> 

scala> val two = one + x5
two: Int = 2

scala> 

scala> // handling generic wildcard arrays (#2386)

scala> // It's put here because type feedback is an important part of it.

scala> val xs: Array[_] = Array(1, 2)
xs: Array[_] = Array(1, 2)

scala> xs.size
res2: Int = 2

scala> xs.head
res3: Any = 1

scala> xs filter (_ == 2)
res4: Array[_] = Array(2)

scala> xs map (_ => "abc")
res5: Array[java.lang.String] = Array(abc, abc)

scala> xs map (x => x)
res6: scala.collection.mutable.ArraySeq[_] = ArraySeq(1, 2)

scala> xs map (x => (x, x))
res7: Array[(_$1, _$1)] forSome { type _$1 } = Array((1,1), (2,2))

scala> 

scala> // interior syntax errors should *not* go into multi-line input mode.

scala> // both of the following should abort immediately:

scala> def x => y => z
<console>:1: error: '=' expected but '=>' found.
       def x => y => z
             ^

scala> [1,2,3]
<console>:1: error: illegal start of definition
       [1,2,3]
       ^

scala> 

scala> 

scala> // multi-line XML

scala> <a>
<b
  c="c"
  d="dd"
/></a>
res8: scala.xml.Elem = 
<a>
<b c="c" d="dd">

scala> 

scala> 

scala> /*
  /*
    multi-line comment
  */
*/

scala> 

scala> 

scala> // multi-line string

scala> """
hello
there
"""
res9: java.lang.String = 
"
hello
there
"

scala> 

scala> (1 +   // give up early by typing two blank lines


You typed two blank lines.  Starting a new command.

scala> // defining and using quoted names should work (ticket #323)

scala> def `match` = 1 
match: Int

scala> val x = `match` 
x: Int = 1

scala> 

scala> // multiple classes defined on one line

scala> sealed class Exp; class Fact extends Exp; class Term extends Exp
defined class Exp
defined class Fact
defined class Term

scala> def f(e: Exp) = e match {  // non-exhaustive warning here
  case _:Fact => 3
}
<console>:18: warning: match is not exhaustive!
missing combination            Exp
missing combination           Term

       def f(e: Exp) = e match {  // non-exhaustive warning here
                       ^
f: (e: Exp)Int

scala> 

scala> 
plusOne: (x: Int)Int
res0: Int = 6
res1: java.lang.String = after reset
<console>:8: error: not found: value plusOne
              plusOne(5) // should be undefined now
              ^