I am always +1 on supporting Java syntax when practical.
> On Apr 29, 2018, at 5:17 PM, MG <[email protected]> wrote:
>
> 2) I feel { { } } being interpreted as an array containing an empty closure
> is confusing, i.e. not least surprise. I would rather not see it cut it so
> close with regards to what the Parrot parser can handle syntax-wise. What do
> others think ?
I don't like it either, but I would be willing to live with it since I'll never
generate something like that myself.
>
> 3) After introducing this syntax extension, what will be considered the
> "Groovy way" of initializing an array in the future ? Is it still
> final int[] a = [ 1, 1, 2, 3, 5, 8 ] as int[]
> or
> final int[] a = { 1, 1, 2, 3, 5, 8 }
> ?
While we are at it, could we just do:
int[] a = [ 1, 1, 2, 3, 5, 8 ]
without the "as int[]" at the end? That would seem to be the "Grooviest" way
IMO.
Cheers,
Keith
> In the 2nd case I would be worried that the core Groovy syntax becomes all
> over the place over time, same as with the new Java lambda syntax (though
> less pronounced, since using/initializing arrays is typically rare).
>
> 4) I am not too worried about the breaking edge cases, because I feel they
> are quite rare in practice, the compiler catches them, and they are easy to
> fix.
>
> Cheers,
> mg
>
>
>
> On 29.04.2018 15:29, Paul King wrote:
>> +1
>>
>> For completeness, I added some more details about the breaking changes and
>> workarounds into the issue - included below for easy reading.
>>
>> Cheers, Paul.
>>
>> =================
>>
>> Groovy currently "promotes" a singleton instance of an object into an array
>> for assignments, e.g.:
>>
>> Integer[] nums = 42
>> assert nums instanceof Integer[]
>> assert nums.size() == 1
>> assert nums[0] instanceof Integer
>>
>> This aligns with how Groovy behaves if you try to call `.each{}` on a
>> non-aggregate. It treats it like a singleton collection and "iterates" over
>> the one item.
>>
>> The existing behavior also currently works for singleton Closures:
>>
>> Closure[] fns0 = { }
>> assert fns0 instanceof Closure[]
>> assert fns0.size() == 1
>> assert fns0[0] instanceof Closure
>>
>> To add support for Java array notation, we will need to partially disable
>> this behavior. The proposed change involves smart parsing, e.g. it will
>> distinguish cases which must be an array and cases which must be a closure
>> but there are some degenerate edge cases which will become breaking changes.
>>
>> The case with the empty closure above will no longer work, instead you will
>> get this behavior, i.e. an empty array is given precedence over an empty
>> closure:
>>
>> Closure[] fns1 = { }
>> assert fns1 instanceof Closure[]
>> assert fns1.size() == 0
>>
>> To get the old behavior back you have a couple of options. Firstly, you can
>> provide the explicit closure argument delimiter:
>>
>> Closure[] fns2 = { -> } // can't be an array
>> assert fns2 instanceof Closure[]
>> assert fns2.size() == 1
>> assert fns2[0] instanceof Closure
>>
>> Or don't rely on singleton promotion and explicitly provide also the array
>> curly braces:
>>
>> Closure[] fns3 = { { } }
>> assert fns3 instanceof Closure[]
>> assert fns3.size() == 1
>> assert fns3[0] instanceof Closure
>>
>> Similarly, for the case of the identity closure:
>>
>> Closure[] fns4 = { it }
>>
>> Previously this worked but under this proposal will give:
>>
>> groovy.lang.MissingPropertyException: No such property: it ...
>>
>> Your options are to add the extra array braces as per above, or use explicit
>> params, e.g.:
>>
>> Closure[] fns5 = { it -> it }
>> assert fns5 instanceof Closure[]
>> assert fns5.size() == 1
>> assert fns5[0] instanceof Closure
>>
>> Alternatively, for this special case you have the following additional
>> option:
>>
>> Closure[] fns6 = Closure.IDENTITY
>> assert fns6 instanceof Closure[]
>> assert fns6.size() == 1
>> assert fns6[0] instanceof Closure
>>
>> There are other cases as well, e.g. this code which currently creates a
>> closure array containing a closure returning the integer 0:
>>
>> Closure[] fns7 = { 0 }
>>
>> will no longer be supported and will fail with:
>>
>> org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast
>> object '0' with class 'java.lang.Integer' to class 'groovy.lang.Closure'
>> The solutions are similar to previously (explicit delimiter):
>>
>> Closure[] fns8 = { -> 0 }
>>
>> or (explicit outer array braces):
>>
>> Closure[] fns9 = { { 0 } }
>>
>>
>> On Sun, Apr 29, 2018 at 8:37 PM, Daniel.Sun <[email protected]
>> <mailto:[email protected]>> wrote:
>> Hi all,
>>
>> As we all know, Java array is one of features widely applied in Java
>> projects. In order to improve the compatibility with Java(Copy & Paste). The
>> PR[1] will make Groovy support java-like array and make the differences[2]
>> with Java less and less, e.g.
>>
>> *One-Dimensional array*
>> ```
>> String[] names = {'Jochen', 'Paul', 'Daniel'}
>> ```
>>
>> *Two-Dimensional array*
>> ```
>> int[][] data = {
>> {1, 2, 3},
>> {4, 5, 6},
>> {7, 8, 9},
>> new int[] { 10, 11, 12 },
>> {13, 14, 15}
>> }
>> ```
>>
>> *Annotation array*
>> ```
>> @PropertySources({
>> @PropertySource("classpath:1.properties"),
>> @PropertySource("file:2 <file:///2>.properties")
>> })
>> public class Controller {}
>> ```
>>
>> *More examples*
>> Please see the examples on the PR page[1]
>>
>> *Known breaking changes*
>> 1. Closure array in the dynamic mode
>> Before
>> ```
>> Closure[] y = { {-> 1 + 1 } }
>> assert y[0].call().call() == 2
>> ```
>> After
>> ```
>> Closure[] y = { {-> 1 + 1 } }
>> assert y[0].call() == 2
>> ```
>> 2. String array in the dynamic mode
>> Before
>> ```
>> String[] a = {}
>> assert 1 == a.length
>> assert a[0].contains('closure')
>> ```
>> After
>> ```
>> String[] a = {}
>> assert 0 == a.length
>> ```
>>
>>
>> If Groovy 3 supports Java-like array, what do you think about the new
>> feature? Do you like it? We need your feedback. Thanks in advance!
>>
>> [+1] I like it
>> [ 0] Not bad
>> [-1] I don't like it, because...
>>
>> Cheers,
>> Daniel.Sun
>> [1] https://github.com/apache/groovy/pull/691
>> <https://github.com/apache/groovy/pull/691>
>> [2] http://groovy-lang.org/differences.html
>> <http://groovy-lang.org/differences.html>
>>
>>
>>
>>
>> --
>> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Users-f329450.html
>> <http://groovy.329449.n5.nabble.com/Groovy-Users-f329450.html>
>>
>
----------------------
Keith Suderman
Research Associate
Department of Computer Science
Vassar College, Poughkeepsie NY
[email protected]
