On Tue, 2008-12-02 at 08:50 +0100, Carl Mäsak wrote: > Darren (>): > > Bit > > Blob > > Set > > Bag > > Mapping > > > > How does one write anonymous value literals of those types? And I mean > > directly, not by writing a literal of some other type and using a conversion > > function to derive the above? > > Why is the latter method insufficient for your needs?
Efficiency reasons, among others. We can quibble over the syntax, but it would be awfully nice if implementations were able to generate the data structure as early as possible -- at compile time (for literals containing only constants) or during runtime as a single build pass rather than build-other-type-then-convert (for literals containing runtime-evaluated expressions). If there isn't an easy way for the implementation to make this optimization, then we're stuck with some of the "basic" types taking twice the time and space to create that other similar types do, for no good reason. Mind you, some implementations may get "lucky" by using a common all-powerful collection implementation underneath, and turning the "conversion" into a simple type relabel (constant cost in time and space), but that doesn't generalize to highly-tuned implementations that optimize each collection type's data structures individually. -'f
