C#: Refactoring a Reynolds number calculator

Question

Hi, I'm trying to learn some C# over the weekend and am following the 15 exercises found here: http://www.jobsnake.com/seek/articles/index.cgi?openarticle&8533

Yesterday I asked a similar question for the Fibonacci sequence and received some great responses which introduced me to elements of C# which I'd not encountered before: http://stackoverflow.com/questions/406446/refactoring-fibonacci-algorithm

Today I would like to see how a C# Jedi would refactor the following code:

static string Reynolds(int d, int v, int rho, int mu)
{
 int number = (d*v*rho) / mu;
 if (number < 2100) return "Laminar Flow";
 else if (number < 2100 && number < 4000) return "Transient Flow";
 else return "Turbulent Flow";
}

So more simple than yesterday, but is there any nice way to deal with the multiple conditionals?

Regards,

Chris

Answer 1

Using the C# ternary operator,

   static string Reynolds(int d, int v, int rho, int mu)
    {        
       int number = (d*v*rho) / mu; 
       return number <  2100? "Laminar Flow":
              number >= 4000? "Turbulent Flow":
                              "Transient Flow";
    }

or, (to give my sarcastic side a bit of free rein), if you find this not readable, you could add comments, to make it more readable,

static string Reynolds(int d, int v, int rho, int mu)
{        
   int number = (d*v*rho) / mu; 
   return /*IF*/ number <  2100? /*Then*/ "Laminar Flow":
          /*IF*/ number >= 4000? /*Then*/ "Turbulent Flow":
                                 /*Else*/ "Transient Flow";
}

Does anyone really think that helps?

Answer 2

I think there is an error in your code but I made an assumption. Your second "if" would never evaluate tree as number < 2000 already makes the first branch true.

I would create an ENUM:

enum FlowType
{
    Laminar
    , Transient
    , Turbulent
};


static FlowType Reynolds(int d, int v, int rho, int mu)
{
    int n = (d*v*rho) / mu;

    if(n < 2000)
    {
        return FlowType.Laminar;
    }
    else if(n < 4000)
    {
        return FlowType.Transient;
    }
    else
    {
        return FlowType.Turbulent;
    }
}