Consider operator proposal

[Marek Kozieł]

AUTHOR: Lasu aka Marek Kozieł

OVERVIEW

FEATURE SUMMARY:
Consider operator extends language with full value support and assign value
to name and return it.

MAJOR ADVANTAGE:
It introduces natural division in variables and values.
It makes language to be more natural for human and generics easier to use.

MAJOR BENEFIT(s):
If we need to get a value, we can do that quite simple (without splitting
expression or duplicating code).
Decrease number of potential bugs (value cannot be assigned).
It can help in splitting code to proper parts; nowdays, we need to declare
variable regardless we need it or not (or make it final).
Decrease size of unnecessary code.
Method can be itself multi-thread with this, but it's far future.


MAJOR DISADVANTAGE:
Possibility to be unclear at start.

ALTERNATIVES:
Some time 'final' variables can be used, but it's more like for-each, life
is better with it.


EXAMPLES

SIMPLE EXAMPLE:
  public static void standard(Resource<String,Container<Unit>> resource) {
    Comparator<Resource<String,Container<Unit>>> resourceComparator
      = (standard? Resource.baseComparator : Resource.extdComparator);
    if (resourceComparator.compare(resource,this.last)==0) return; //
duplicate
    ...
  }

  public static void consider(Resource<String,Container<Unit>> resource) {
    (standard? Resource.baseComparator : Resource.extdComparator) ::
resourceComparator;
    if (resourceComparator.compare(resource,this.last)==0) return; //
duplicate
    ...
  }

  public static void standard_2(ArrayList<Resource<String,Container<Unit>>>
resources){
    for (Resource<String,Container<Unit>> resource: resources){
      System.out.println(resource);
    }
  }

  public static void consider_2(ArrayList<Resource<String,Container<Unit>>>
resources){
    for (::resource:resources){
      System.out.println(resource);
    }
  }


ADVANCED EXAMPLE:
  public void validLastElementState(ArrayList<Data> list){
    if
(list.get(list.size()::size-1)::data.reportStare().getState()!=validState){
      throw new IllegalStateException(Data.class.getSimpleName()+"("+data+")
of "+size+" elements is in wrong "+State.class.getSimpleName());
    }
    ... other operations ...
  }

> Would be compiled to:
  public void validLastElementState(ArrayList<Data> list){
    {
      list.size()::size;
      list.get(size-1)::data
      if (data.reportStare().getState()!=validState){
        throw new IllegalStateException(
          Data.class.getSimpleName()+"("+data+") of "+size+" elements is in
wrong "+State.class.getSimpleName());
      }
    }
  ... other operations ...
  }
DETAILS

SPECIFICATION:
Value :: name
Assign left side value to given name and return it.
JLS 14.14.2:
http://java.sun.com/docs/books/jls/third_edition/html/statements.html#14.14.2
EnhancedForStatement:
  for ( VarDeclaration : Expression) Statement

VarDeclaration: al least one of
  VariableDeclaration
  ValueDeclaration

VariableDeclaration
  VariableModifiersopt Type Identifier

ValueDeclaration
  :: ValueName


COMPILATION:
While value is same as final variable compiling is not big problem.

TESTING:
Same as final variable.

LIBRARY SUPPORT:
No.

REFLECTIVE APIS:
No.

OTHER CHANGES:
No.

MIGRATION:
No need.

COMPATIBILITY
Compiled code can be normally executed.

REFERENCES
Consider operator proposal:
http://lasu2string.blogspot.com/2009/03/consider-operator-proposal.html


-- 
Pozdrowionka. / Regards.
Lasu aka Marek Kozieł

http://lasu2string.blogspot.com/