Re: macros (was: Seeking computer-programming job (Sunnyvale, CA))

From:
Lew <lew@lewscanon.com>
Newsgroups:
comp.lang.lisp,comp.lang.java.programmer
Date:
Fri, 15 May 2009 07:34:26 -0700 (PDT)
Message-ID:
<5fb30931-4310-4e77-a967-460539bf9248@n8g2000vbb.googlegroups.com>
Stefan Ram wrote:

  The same coded in Java without macros /is/ more verbose,
  but also more readable to someone who knows Java:

public static String getMultiValue( Object valueObject )
{ String result = null;
  if( valueObject == null )result = null;

  else if( valueObject instanceof StringValue )
  { StringValue stringValue =( StringValue )valueObject;
    result = getStringValue( stringValue ); }

  else if( valueObject instanceof SprayValue )
  { SprayValue setValue =( SprayValue )valueObject;
    result = getSetValue( setValue ); }

  return result; }


An experienced Java programmer will see this series of 'instanceof'
operators and look for a way to code the thing polymorphically.

 interface Multi<T>
 {
   public String getValue( T arg );
 }
 class StringVersion implements Multi<String>
 {
   public String getValue( String arg )
   {
     return getStringValue( arg );
   }
 }
 class SprayVersion implements Multi<Spray>
 {
   public String getValue( Spray arg )
   {
    return getSprayValue( arg );
   }
 }

etc.

--
Lew

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