Exercise C# input/output

• Reading (writing) numbers into (out of) your C# program using command-line, standard streams, and file streams.

Tasks:

1. Command-line

   Read a set of numbers from the command-line argument in the form of a comma-separated list (we follow the option convention of mcs) like this,

   mono main.exe -numbers:1,2,3,4,5 > Out.txt
   	

   and print these numbers together with their sines and cosines (in a table form) to the standard output. Something like

   public static void Main(string[] args){
   foreach(var arg in args){
   	var words = arg.Split(':');
   	if(words[0]=="-numbers"){
   		var numbers=words[1].Split(',');
   		foreach(var number in numbers){
   			double x = double.Parse(number);
   			WriteLine($"{x} {Sin(x)} {Cos(x)}");
   			}
   		}
   	}
   }
   

   The program can get the numbers from the command-line directly,

   mono main.exe -numbers:1,2,3,4,5 > out.txt
   

   or, alternatively, if the line of numbers is too long, one can write the numbers into a file and then "cat" the file into the command line,

   echo "-numbers:1,2,3,4,5" > inputfile
   mono main.exe $$(cat inputfile) > out.txt # double dollar-sign if in Makefile
   

   The length of the command line is limited though, so the size of the file should not exceed your command line limit (probably about 2 megabytes).

2. Standard input stream

   Read a sequence of numbers, separated by a combination of blanks (' '), tabs ('\t'), and newline characters ('\n'), from the standard input and print these numbers together with their sines and cosines (in a table form) to the standard error. Something like

   char[] split_delimiters = {' ','\t','\n'};
   var split_options = StringSplitOptions.RemoveEmptyEntries;
   for( string line = ReadLine(); line != null; line = ReadLine() ){
   	var numbers = line.Split(split_delimiters,split_options);
   	foreach(var number in numbers){
   		double x = double.Parse(number);
   		Error.WriteLine($"{x} {Sin(x)} {Cos(x)}");
                   }
           }
   

   The program can be run as

   echo 1 2 3 4 5 | mono main.exe 2> out.txt
   

   or

   echo 1 2 3 4 5 > input.txt
   mono main.exe < input.txt 2> out.txt
   

   or

   echo 1 2 3 4 5 > input.txt
   cat input.txt | mono stdin.exe 2> out.txt
   

3. File streams

   Read a set of numbers separated by newline characters from "inputfile" and write them together with their sines and cosines (in a table form) to "outputfile". The program must read the names of the "inputfile" and "outputfile" from the command-line,

   mono main.exe -input:input.txt -output:out.txt
   

   Something like

   string infile=null,outfile=null;
   foreach(var arg in args){
   	var words=arg.Split(':');
   	if(words[0]=="-input")infile=words[1];
   	if(words[0]=="-output")outfile=words[1];
   	}
   if( infile==null || outfile==null) {
   	Error.WriteLine("wrong filename argument");
   	return 1;
   	}
   var instream =new System.IO.StreamReader(infile);
   var outstream=new System.IO.StreamWriter(outfile,append:false);
   for(string line=instream.ReadLine();line!=null;line=instream.ReadLine()){
   	double x=double.Parse(line);
   	outstream.WriteLine($"{x} {Sin(x)} {Cos(x)}");
           }
   instream.Close();
   outstream.Close();