scala的collect 方法 其实没有俺么难

scala> List(1, 2, 3, 4, 5, 6) collect { case i if i % 2 == 0 => i * i }
res0: List[Int] = List(4, 16, 36)


scala> List(1, 2, 3, 4, 5, 6) collect { case i if i % 2 == 0 => i+1 }
res1: List[Int] = List(3, 5, 7)


scala> List(1, 2, 3, 4, 5, 6) collect { case i  => i+1 }
res2: List[Int] = List(2, 3, 4, 5, 6, 7)


scala> List(1, 2, 3, 4, 5, 6) collect { case i  =>(i, i+1 )}
res3: List[(Int, Int)] = List((1,2), (2,3), (3,4), (4,5), (5,6), (6,7))


scala> List(1, 2, 7, 4, 9, 6) collect { case i  =>(i, i+1 )}
res4: List[(Int, Int)] = List((1,2), (2,3), (7,8), (4,5), (9,10), (6,7))


scala> List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;i)=> i * i }
<console>:1: error: ')' expected but ';' found.
       List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;i)=> i * i }
                                                        ^
<console>:1: error: ';' expected but ')' found.
       List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;i)=> i * i }
                                                          ^


scala> List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;true)=> i * i }
<console>:1: error: ')' expected but ';' found.
       List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;true)=> i * i }
                                                        ^
<console>:1: error: ';' expected but ')' found.
       List(1, 2, 3, 4, 5, 6) collect { case i if (i=i+1;true)=> i * i }
                                                             ^


scala> List(1, 2, 3, 4, 5, 6) collect { case i if {i=i+1;true}=> i * i }
<console>:8: error: reassignment to val
              List(1, 2, 3, 4, 5, 6) collect { case i if {i=i+1;true}=> i * i }
                                                           ^


scala> List(1, 2, 3, 4, 5, 6) collect { case i if {i+1;true}=> i * i }
res6: List[Int] = List(1, 4, 9, 16, 25, 36)


scala>