Re: guard clause style static if

[kdevel via Digitalmars-d-learn]

On Saturday, 7 July 2018 at 11:56:40 UTC, rikki cattermole wrote:
On 07/07/2018 11:44 PM, kdevel wrote:
On Saturday, 7 July 2018 at 11:29:35 UTC, rikki cattermole 
wrote:
       static if (args.length == 0)
          return;

else {


       writeln (args [0]);
       return bar (args [1 .. $]);

}

That's not guard clause style [1][2].

[1] 
https://refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html

[2] http://wiki.c2.com/?GuardClause

Neither was your original example.

My example was

   void bar (T ...) (T args)
   {
      static if (args.length == 0) // 3
         return;                   // 4

      writeln (args [0]);
      return bar (args [1 .. $]);
   }

The guard clause is in lines 3 and 4.

"A method has conditional behavior that does not make clear 
what the normal path of execution is"

In my example one immediately spots the "normal path of 
execution". Your
proposal

   void bar (T ...) (T args)
   {
      static if (args.length == 0)
         return;
      else {
        writeln (args [0]);
        return bar (args [1 .. $]);
      }
   }

leads to unreadable arrow code [3].

   void bar (T ...) (T args) if (T.length == 0)
   {
      return;
[removed]
   }

   void bar (T ...) (T args) if (T.length > 0)
   {
      writeln (args [0]);
      return bar (args [1 .. $]);
   }

Interesting alternative but using template constraints introduces 
code repetition: If you want to add another special case, say 
length == 4, you have to repeat the logical complement in the 
"else" branch:

    void bar (T ...) (T args) if (T.length == 0)
    {
       return;
    }

    void bar (T ...) (T args) if (T.length == 4)
    {
    // some code
    }

    void bar (T ...) (T args) if (T.length > 0 && T.length != 4)
    {
       writeln (args [0]);
       return bar (args [1 .. $]);
    }

[3] https://blog.codinghorror.com/flattening-arrow-code/