Proposal: Indexing access syntax for Lists and Maps

[rssh at gradsoft.com.ua]

> Indexing access syntax for Lists and Maps
>
> VERSION
> This is version 1.0.
>
> AUTHOR(S):
> Shams Mahmood Imam
>
> OVERVIEW
>
> FEATURE SUMMARY:
> Collection classes are among the most frequently used in the Java SDK.
> Currently Lists and Maps do not provide any additional language
> feature to access individual elements unlike Arrays. This proposal
> aims to provide these Collection citizens of java additional
> language support to access elements like Arrays have currently.
>
> MAJOR ADVANTAGE:
> Will provide a consistent syntax for accessing elements of Arrays,
> Lists and Maps. In addition, the language grammar will not change

 Often we nee something 'less' than List or Map.
I. e. I would be good to see i additional to lists and maps some 'minimal'
get/set interface.

> much since the subscript operator is already supported for Arrays.
>

....
> DETAILS
>
> SPECIFICATION:
> Java Language Specification changes:
>
> 15.29 (NEW CHAPTER): Collection Access Expressions
> A collection access expression contains two subexpressions, the List/Map
> reference expression (before the left bracket) and the index expression
> (within the brackets). Note that the List/Map reference expression may be
> a name or any expression that evaluates to a List/Map. The index
> experssion is expected to evaluate to an int for Lists and a valid key
> type for Maps.
>
> CollectionAccess:
>   Expression [ Expression ]
>
> 15.8 Primary Expressions
> original:
> ---------
> PrimaryNoNewArray:
>   Literal
>   Type . class
>   void . class
>   this
>   ClassName.this
>   ( Expression )
>   ClassInstanceCreationExpression
>   FieldAccess
>   MethodInvocation
>   ArrayAccess
>
> replaced with:
> --------------
> PrimaryNoNewArray:
>   Literal
>   Type . class
>   void . class
>   this
>   ClassName.this
>   ( Expression )
>   ClassInstanceCreationExpression
>   FieldAccess
>   MethodInvocation
>   ArrayAccess
>   CollectionAccess
>

 Ara syntax to ArrayAccess and CollectionAccess difer ?
If not, this is one expression in grammar


> 15.26 Assignment Operators
> original:
> ---------
> LeftHandSide:
>   ExpressionName
>   FieldAccess
>   ArrayAccess
>
> replaced with:
> --------------
> LeftHandSide:
>   ExpressionName
>   FieldAccess
>   ArrayAccess
>   CollectionAccess
>

 The same note as previous.

>

Also JLS contains specifivation of behavious of assigment.
I changed this specification for class-array-assigment (in simular
proposal, but more general and annotation-based instead interface-based
as you)
http://docs.google.com/Doc?id=dhhvggr8_18djp85shk

Part of 15.13 and 15.26.1 of JLS must be rewritten in you case. (I guess
you can get this changes from text of my proposal and slightly adopt,
semantics would be the same)



> COMPILATION:
>
> After successful creation of the AST handling the additional grammar for
> Collection Access expressions, the syntactic sugar will be replaced by
> JDK1.4 compatible code during the Code Generation phase. This is
> consistent with how JDK5.0 constructs like the for-each loop is handled by
> the compiler.
>
> e.g.
> public class TestConcise {
>   public static void main(String[] args) {
>     java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
> String>();
>     m1[2] = "two";
>
>     java.util.LinkedList<String> l1 = java.util.Arrays.asList( new
> String[] {"a", "b", "c" });
>     m1[3] = l1[2];
>     l1[0] = m1[0];
>     l1[1] = "one";
>   }
> }
>
> is converted to
> public class TestConcise {
>   public TestConcise() {
>     super();
>   }
>
>   public static void main(String[] args) {
>     java.util.Map<Integer, String> m1 = new java.util.HashMap<Integer,
> String>();
>     m1.put(Integer.valueOf(2), "two");
>
>     java.util.LinkedList<String> l1 = java.util.Arrays.asList( new
> String[] {"a", "b", "c" });
>     m1.put(Integer.valueOf(3), l1.get(2));
>     l1.set(0, m1.get(Integer.valueOf(0)));
>     l1.set(1, "one");
>   }
> }
>
>
> TESTING:
>
> LIBRARY SUPPORT:
> No additional library support is needed.
>
> REFLECTIVE APIS:
> This proposal does not require any reflective API changes.
>
> OTHER CHANGES:
> No changes required.
>
> MIGRATION:
> No migration is needed.
>
> COMPATIBILITY
>
> BREAKING CHANGES:
> No breaking changes.
>
> EXISTING PROGRAMS:
> Existing programs are not affected by this change.
>
> REFERENCES
> My Java7 Wishlist regarding Collections,
> http://shamsmi.blogspot.com/2008/04/my-java7-wishlist-regarding-collections.html
> Implementation of My Java7 Wishlist,
> http://shamsmi.blogspot.com/2008/05/implementation-of-my-java7-wishlist.html
>
> EXISTING BUGS:
> None.
>
> URL FOR PROTOTYPE (optional):
> Projects kijaro's concisecollections branch:
> https://kijaro.dev.java.net/source/browse/kijaro/branches/concisecollections/
>
>
>
>
>