Mismatch between the order of the type variable and the order of the SAM method formal parameters

[Rémi Forax]

On 09/16/2011 01:09 AM, Yuval Shavit wrote:
> Why should the lambda usually come last? I admit I'm fairly new to 
> functional programming, but it seems that functions/lambdas often come 
> first in methods, which can be useful when currying. I realize that 
> currying isn't part of this project, but it's conceivable that Java 
> would have it in the future.

We talk about function that takes a lambda,
because the lambda can have a body split on several lines,
it's usually more readable to put the lambda at the end.

You can compare:
   int sum = list.reduce(0, (sum, s) -> {
     if ("".equals(s)) {
       return 0;
      }
      return 1;
   });

with:
   int sum = list.reduce((sum, s) -> {
      if ("".equals(s)) {
       return 0;
      }
      return 1;
   }, 0);

The argument after the lambda is too far from the beginning of
the method call.

Rémi

>
> On Thu, Sep 15, 2011 at 12:00 PM, Rémi Forax <forax at univ-mlv.fr 
> <mailto:forax at univ-mlv.fr>> wrote:
>
>     On 09/15/2011 05:56 PM, Brian Goetz wrote:
>     > In general, it is best if methods that have a single lambda
>     parameter have the lambda parameter last.
>
>     I agree for Iterable.reduce, but here it's Reducer.reduce().
>
>     Rémi
>
>     >
>     >
>     > On Sep 15, 2011, at 12:30 AM, Rémi Forax wrote:
>     >
>     >> Hi all,
>     >>
>     >> Here is the declaration of a Reducer:
>     >>
>     >>    interface Reducer<T, U>  {
>     >>        U reduce(U base, T t);
>     >>    }
>     >>
>     >> and how to use it:
>     >>
>     >>    Reducer<String, Integer>  reducer = (Integer i, String s) ->
>      i +
>     >> s.length();
>     >>
>     >> As you see the order of the type argument<String, Integer>  is not
>     >> the same as the order of the type of the formal parameter of
>     the lambda
>     >> (Integer i, String s).
>     >> I think it will be simpler if the signature of reduce() was
>     changed to
>     >> swap the two
>     >> formal parameters.
>     >>
>     >> Rémi
>     >>
>     >>
>
>
>