Stream.flatMap signature is not correct (original) (raw)

Remi Forax forax at univ-mlv.fr
Sat Dec 1 15:20:18 PST 2012

On 12/01/2012 06:55 PM, Remi Forax wrote:

On 12/01/2012 06:34 PM, Kevin Bourrillion wrote:

On Fri, Nov 30, 2012 at 8:44 PM, Remi Forax <forax at univ-mlv.fr_ _<mailto:forax at univ-mlv.fr>> wrote:

Stream.flatMap is currently specified as: Stream flatMap(FlatMapper<? super T, ? extends R> mapper); but should be: Stream flatMap(FlatMapper<? super T, ? super R> mapper);

I don't understand. If the mapper produces Numbers how can you return a stream of Integers? sorry, never send a mail Friday evening. Rémi

BTW, the problem of inference is still present:

Arrays.asList(Object.class, String.class).stream().flatMap( (block, clazz) -> { Arrays.asStream(clazz.getFields()).forEach(block); }); // doesn'tcompile

Arrays.asList(Object.class, String.class).stream().flatMap( (Block block, Class clazz) -> { Arrays.asStream(clazz.getFields()).forEach(block); }); // Ok

Also note that it doesn't work with the signature (Block, Class<?>) because Block is a subtype of Block<? super Field>. Rémi

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