Question

我尝试编写类似这样的类定义时遇到多个编译错误。

--auto-gen-config

我收到这样的错误..



    trait BinOps[T] {
      def +(that: Vector[T]): Vector[T]
      def -(that: Vector[T]): Vector[T]
      def *(that: Vector[T]): Vector[T]
      def /(that: Vector[T]): Vector[T]
    }

    trait Vector[T] {
      def toList(): List[T]
      def zeros(length: Int): Vector[T]
    }

    object Vector {
      def apply[T](args: T*): Vector[T] = new VectorImpl[T](args.toList)

      private class VectorImpl[@specialized(Double, Int, Float, Long)T](val _data: List[T])
        extends Vector[T]
        with BinOps[T] {
        def +(that: Vector[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 + elem._2))
        def -(that: Vector[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 - elem._2))
        def *(that: Vector[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 * elem._2))
        def /(that: Vector[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 / elem._2))

        def fill(length: Int, value: T): Vector[T] = new VectorImpl[T](List.fill[T](length)(value))
        def toList(): List[T] = _data.toList
      }

      implicit def VectorToList[T](v: Vector[T]): List[T] = v.toList
    }

然而，做一个zip应该导致一个类型为T的元组，我试图访问第一个和第二个元素。那么我做错了什么？

Answer 1

错误：（37,95）value - 不是类型参数T
的成员

这是真正的错误（关于字符串的错误是#include<stdio.h> #include<string.h> #include<stdlib.h> void main(void) { char str[] = "MyID-MyName-MyAddress-MyNumber--MyAlias"; char * str1, * token; int i = 0; int parsed_buffer_length = 0; char * previous_delimiter_index = str; char * delimiter_index = str; for(;;) { str1 = str+parsed_buffer_length; delimiter_index = strstr(str1,"-"); if(delimiter_index==NULL) { printf("%s",str1); //prints last token break; } token = malloc(delimiter_index-previous_delimiter_index+1); memset(token,'\0',delimiter_index-previous_delimiter_index+1)); strncpy(token,str1,(delimiter_index-previous_delimiter_index)); printf("%s\n",token); parsed_buffer_length = (int)(parsed_buffer_length+delimiter_index-previous_delimiter_index+1); previous_delimiter_index = delimiter_index+1; free(token); } }中隐式转换的不幸结果 - 我建议使用MyID MyName MyAddress MyNumbers MyAlias构建以避免此类误导性错误。你的Predef不受约束 - -Yno-predef应该做什么？例如。如果T是-，那该怎么办？T是什么？所以它不会编译。

Answer 2

上面的所有答案都指向了正确的问题。我将发布最终有效的答案。正如JimN所建议的那样，以及来自scala irc的帮助，这最终对我有用。非常感谢您的解释

import Numeric.Implicits._
import Fractional.Implicits._


trait BinOps[T] {
  def +(that: Vector[T])(implicit ev: Numeric[T]): Vector[T]
  def -(that: Vector[T])(implicit ev: Numeric[T]): Vector[T]
  def *(that: Vector[T])(implicit ev: Numeric[T]): Vector[T]
  def /(that: Vector[T])(implicit ev: Fractional[T]): Vector[T]
}

trait Vector[T] {
  def toList(): List[T]
  def zeros(length: Int)(implicit ev: Numeric[T]): Vector[T]
}


object Vector {
  def apply[T](args: T*): Vector[T] = new VectorImpl[T](args.toList)

  private class VectorImpl[@specialized(Double, Int, Float, Long)T](val _data: List[T])
    extends Vector[T]
    with BinOps[T] {
    def +(that: Vector[T])(implicit ev: Numeric[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 + elem._2))
    def -(that: Vector[T])(implicit ev: Numeric[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 - elem._2))
    def *(that: Vector[T])(implicit ev: Numeric[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 * elem._2))
    def /(that: Vector[T])(implicit ev: Fractional[T]): Vector[T] = new VectorImpl[T](_data.zip(that).map(elem => elem._1 / elem._2))

    def fill(length: Int, value: T): Vector[T] = new VectorImpl[T](List.fill[T](length)(value))
    def zeros(length: Int)(implicit ev: Numeric[T]): Vector[T] = fill(length, ev.zero)
    def toList(): List[T] = _data.toList
  }

  implicit def VectorToList[T](v: Vector[T]): List[T] = v.toList
}

在scala中对泛型类实现二进制操作

2 个答案: