allocate_mapping() - pre-allocate space for a mapping
mapping allocate_mapping( int size );
Returns a mapping with space for 'size' elements preallocated.
int y = 200;
x = allocate_mapping(y);
where y is the initial size of the mapping. Using allocate_mapping is
the preferred way to initalize the mapping if you have some idea of how
many elements the map will contain (200 in this case). The reason is
that allocating storage all at once is slightly more memory efficient.
Thus if you are using mappings to store a soul with 200 entries, the
above initialization would be quite appropriate. Note, that the above
initialization does not restrict you to 200 entries. It just that the
first 200 entries will be stored more efficiently. Note: if you will
be deleting many elements from the mapping, you should use x = () to
initialize the mapping rather than using allocate_mapping().
Note: at this point in time, 'size' is meaningless, x = allocate_map‐
ping(200); is equivalent to x = ([ ]);