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From Paul King <pa...@asert.com.au>
Subject Re: [Poll] About supporting Java-like array
Date Sun, 29 Apr 2018 22:29:55 GMT
The preferred Groovy syntax would probably still remain:

int[] fibs = [1, 1, 2, 3, 5, 8]

Cheers, Paul.

On Mon, Apr 30, 2018 at 7:17 AM, MG <mgbiz@arscreat.com> wrote:

> After thinking about this some more for the last weeks
> +1 with asterisk
> from my side:
>
> 1) I am always for being as Java compatible as possible (though I see that
> this might not be feasible in all cases in the future, due to Java changing
> at a much faster pace and with more syntax changes now than before;
> example: Java considered naming the new "var" keword "def", which is
> similar to but not the same as Java-var in Groovy...)
>
> 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 ?
>
> 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 }
> ?
> 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 <sunlan@apache.org> 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.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
>> [2] http://groovy-lang.org/differences.html
>>
>>
>>
>>
>> --
>> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Users-f329450.html
>>
>
>
>

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