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我想在 scala 中解析一个文件（可能使用 JavaTokerParsers？）。可能不使用太多变量:-)

该文件是光线追踪器的输入。

它是基于行的文件结构。

存在三种类型的行：空行、注释行和命令行

注释行以 # 开头（可能在 # 之前有一些空格）命令行以标识符开头，可选地后跟许多参数（浮点数或文件名）。

我该怎么办。我想解析器被这样调用

val 场景 = parseAll（场景文件，文件）；

示例文件：

#Cornell Box
size 640 480
camera 0 0 1 0 0 -1 0 1 0 45
output scene6.png

maxdepth 5    
maxverts 12
#planar face
vertex -1 +1 0
vertex -1 -1 0
vertex +1 -1 0
vertex +1 +1 0

#cube
vertex -1 +1 +1
vertex +1 +1 +1
vertex -1 -1 +1
vertex +1 -1 +1

vertex -1 +1 -1
vertex +1 +1 -1
vertex -1 -1 -1
vertex +1 -1 -1


ambient 0 0 0
specular 0 0 0
shininess 1
emission 0 0 0
diffuse 0 0 0

attenuation 1 0.1 0.05

point 0 0.44 -1.5 0.8 0.8 0.8
directional 0 1 -1 0.2 0.2 0.2

diffuse 0 0 1
#sphere 0 0.8 -1.5 0.1


pushTransform

#red
pushTransform
translate 0 0 -3
rotate 0 1 0 60
scale 10 10 1
diffuse 1 0 0
tri 0 1 2
tri 0 2 3
popTransform

#green
pushTransform
translate 0 0 -3
rotate 0 1 0 -60
scale 10 10 1
diffuse 0 1 0
tri 0 1 2
tri 0 2 3
popTransform

#back
pushTransform
scale 10 10 1
translate 0 0 -2
diffuse 1 1 1
tri 0 1 2
tri 0 2 3
popTransform

#sphere
diffuse 0.7 0.5 0.2
specular 0.2 0.2 0.2
pushTransform
translate 0 -0.7 -1.5
scale 0.1 0.1 0.1
sphere 0 0 0 1
popTransform

#cube
diffuse 0.5 0.7 0.2
specular 0.2 0.2 0.2
pushTransform
translate -0.25 -0.4 -1.8
rotate 0 1 0 15
scale 0.25 0.4 0.2
diffuse 1 1 1

tri 4 6 5
tri 6 7 5
tri 4 5 8
tri 5 9 8
tri 7 9 5
tri 7 11 9
tri 4 8 10
tri 4 10 6
tri 6 10 11
tri 6 11 7
tri 10 8 9
tri 10 9 11
popTransform

popTransform

popTransform
4

1 回答 1

3

也许我对一个班轮太用力了，但这是我的看法（尽管习惯上它可能不是最佳的）：

首先，CommandParams以列表格式表示一个命令及其参数。如果没有参数，那么我们有Noneargs：

case class CommandParams(command:String, params:Option[List[String]])

然后是文件解析和构造一行以及逐行解释：

val fileToDataStructure = Source.fromFile("file.txt").getLines()    //open file and get lines iterator
  .filter(!_.isEmpty)   //exclude empty lines
  .filter(!_.startsWith("#"))   //exclude comments
  .foldLeft(List[CommandParams]())    //iterate and store in a list of CommandParams
  {(listCmds:List[CommandParams], line:String) =>   //tuple of a list of objs so far and the current line
                    val arr = line.split("\\s")   //split line on any space delim
                    val command = arr.head    //first element of array is the command
                    val args = if(arr.tail.isEmpty) None else Option(arr.tail.toList)   //rest are their params
                    new CommandParams(command, args)::listCmds   //construct the obj and cons it to the list
  }
  .reverse    //due to cons concat we need to reverse to preserve order

遍历它的演示输出：

fileToDataStructure.foreach(println)

产量：

CommandParams(size,Some(List(640, 480)))
CommandParams(camera,Some(List(0, 0, 1, 0, 0, -1, 0, 1, 0, 45)))
CommandParams(output,Some(List(scene6.png)))
CommandParams(maxdepth,Some(List(5)))
CommandParams(maxverts,Some(List(12)))
CommandParams(vertex,Some(List(-1, +1, 0)))
...
CommandParams(pushTransform,None)
CommandParams(pushTransform,None)
CommandParams(translate,Some(List(0, 0, -3)))
...

加载后如何迭代它以执行实际工作的演示：

fileToDataStructure.foreach{
  cmdParms => cmdParms match {
    case CommandParams(cmd, None) => println(s"I'm a ${cmd} with no args")
    case CommandParams(cmd, Some(args))=> println(s"I'm a ${cmd} with args: ${args.mkString(",")}")
  }
}

产生输出：

I'm a size with args: 640,480
I'm a camera with args: 0,0,1,0,0,-1,0,1,0,45
I'm a output with args: scene6.png
I'm a maxdepth with args: 5
I'm a maxverts with args: 12
I'm a vertex with args: -1,+1,0
...
I'm a popTransform with no args
I'm a popTransform with no args
于 2013-11-07T10:30:50.810 回答