3
我剛開始玩Scala,並一直使用Michel Schinz的「Scala By Example」(http://www.scala-lang.org/node/198)作爲起點。在特質部分,我試圖使用反射/方法調用來測試特性,並想測試所有的比較運算符。我遇到了這個問題,並在NameTransformer中爲操作員找到了解決方案。但是,!=運算符在我看來並不會轉換爲等效函數,如<,< =,>,> = =等於。我想知道是否有辦法調用!=很像其他我沒有發現的操作符?如何在對象上調用'!='方法?
從PDF:
trait ord {
def < (that:Any):Boolean
def <= (that:Any):Boolean = (this < that) || (this == that)
def > (that:Any):Boolean = !(this <= that)
def >= (that:Any):Boolean = !(this < that)
}
class Date(y:Int, m:Int, d:Int) extends ord{
def year = y
def month = m
def day = d
override def toString():String = year + "-" + month + "-" + day
override def equals(that:Any): Boolean =
that.isInstanceOf[Date] && {
val o = that.asInstanceOf[Date]
o.day == this.day && o.month == this.month && o.year == this.year
}
override def <(that:Any):Boolean = {
if (!that.isInstanceOf[Date])
error("Cannot compare " + that + " and date")
val o = that.asInstanceOf[Date]
(year < o.year) ||
(year == o.year && (month < o.month ||
(month == o.month && day < o.day)))
}
}
我的代碼:
def Classes_Traits(){
val (d1, d2, d3) = (new Date(2001, 10, 1), new Date(2001, 10, 1), new Date(2000, 1, 10))
println("d1 : " + d1)
println("d2 : " + d2)
println("d3 : " + d3)
Array((d1,d2), (d2,d3), (d3,d1)).foreach {
(comp:(Date, Date)) =>
println("comparing " + comp._1 + " and " + comp._2)
val d = comp._1.getClass()
Map(
"equals " -> "equals",
"not equals " -> "!=",
"less than " -> "<",
"less than or equal" -> "<=",
"more than " -> ">",
"more than or equal" -> ">=").foreach {
(a) =>
println(a._1 + " : " +
d.getMethod(scala.reflect.NameTransformer.encode(a._2),
classOf[Object]).invoke(comp._1, comp._2))
}
/*println("equals : " + m.invoke(comp._1, comp._2))
// Same as above
println(comp._1 + " == " + comp._2 + " is " + (comp._1 == comp._2))
println(comp._1 + " != " + comp._2 + " is " + (comp._1 != comp._2))
println(comp._1 + " > " + comp._2 + " is " + (comp._1 > comp._2))
println(comp._1 + " >= " + comp._2 + " is " + (comp._1 >= comp._2))
println(comp._1 + " < " + comp._2 + " is " + (comp._1 < comp._2))
println(comp._1 + " <= " + comp._2 + " is " + (comp._1 <= comp._2))
*/
}
}
例外: 比較2001年10月1日和2001年10月1日 大於或等於:真比 更多:假
Exception in thread "main" java.lang.NoSuchMethodException: proj2.Main$Date.$bang$eq(java.lang.Object)
at java.lang.Class.getMethod(Class.java:1605)
at proj2.Main$$anonfun$Classes_Traits$1$$anonfun$apply$1.apply(Main.scala:180)
at proj2.Main$$anonfun$Classes_Traits$1$$anonfun$apply$1.apply(Main.scala:178)
at scala.collection.immutable.HashMap$HashMap1.foreach(HashMap.scala:125)
at scala.collection.immutable.HashMap$HashTrieMap.foreach(HashMap.scala:344)
at proj2.Main$$anonfun$Classes_Traits$1.apply(Main.scala:177)
at proj2.Main$$anonfun$Classes_Traits$1.apply(Main.scala:168)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:34)
at scala.collection.mutable.ArrayOps.foreach(ArrayOps.scala:35)
at proj2.Main$.Classes_Traits(Main.scala:167)
at proj2.Main$.main(Main.scala:26)
at proj2.Main.main(Main.scala)
謝謝。我將更多地關注'=='和'!='的特殊編譯器。指點在哪裏讀取它們是受歡迎的。 – 2011-06-13 15:59:41
我想說,對於這些問題,編譯小片段並查看生成的字節碼是理解編譯器的最佳方式。或者,查看編譯器的源代碼... – 2011-06-13 18:54:53