array copy/ref question

[Jesse Phillips]

On Mon, 11 Aug 2008 21:20:32 -0400, Brian Sturk wrote:

> Lars Ivar Igesund Wrote:
> 
>> Brian Sturk wrote:
>> 
>> > I'm trying to get a handle on the array assignment, slicing
>> > operations and am a little confused.  The last copy gives me an
>> > "overlapping array copy".
>> >  Both arrays have a length of 4.  Is it that I cannot copy from one
>> > dynamic array to another (even if the same size)?
>> 
>> It means you are trying to copy from the same memory you are copying to
>> - your arrays reference the same memory.
> 
> Hi there,
> 
> Thanks for the clarification, sounds like I need to do a memcpy to do a
> true copy.
> 
> ~telengard

The problem is at the top of the program, this should give you the same 
error:

main( string[] args )
{
    int[] test = [ 1, 2, 3, 4 ];
    int[] copy;

    copy = test;

    test[1] = 7;

    writefln( "Ref: test[1] %d copy[1] %d", test[1], copy[1] );

    assert( test[1] == 7 );
    assert( copy[1] == 7 );

    copy    = test[];
    test[1] = 9;

    assert( test[1] == 9 );
    assert( copy[1] == 9 );

    writefln( "Alt ref syntax: test[1] %d copy[1] %d", test[1], copy[1] );

    writefln( "%d %d", test.length, copy.length );

    copy[]  = test;     /* Want to copy, get Error: overlapping array copy
    */ test[1] = 11;

    assert( test[1] == 11 );
    assert( copy[1] == 9 );

    writefln( "Copy: test[1] %d copy[1] %d", test[1], copy[1] );
}

You created copy and told it to point to test, you would need to 
initialize copy to its own memory.

main( string[] args )
{
    int[] test = [ 1, 2, 3, 4 ];
    int[] copy = new int[4];

    copy[]  = test;     
    test[1] = 11;

    assert( test[1] == 11 );
    assert( copy[1] == 2 );

    writefln( "Copy: test[1] %d copy[1] %d", test[1], copy[1] );
}