subject:"Re\: DGM for first or default"

Re: DGM for first or default

2019-02-17 Thread Milles, Eric (TR Tech, Content & Ops)

Thanks for the note on 2.5 and the v8 methods.


I considered withDefault, but yes the mutation was a deal breaker and it only 
works for List and Map.  If I use Optional, then the case of null as a member 
of the collection becomes an issue to deal with.  Adding a bevy of new DGMs is 
not ideal either.  This is a tough one; I might end up sticking with "iterable 
? iterable.first() : defaultValue" for now.


I would like to submit for future consideration that it would be nice to be 
able to control getAt's choice to return null if the given index is out of 
range.  This to me is the more general solution.


From: Paul King 
Sent: Sunday, February 17, 2019 6:07 PM
To: Groovy_Developers
Subject: Re: DGM for first or default

Groovy 2.5 still has JDK 7 as minimum whereas Groovy 3.0 has 8 as minimum. You 
can still add DGM methods into 
org.codehaus.groovy.vmplugin.v8.PluginDefaultGroovyMethods and then they will 
only be available when running on a JDK8+ VM.

Wrt to the question of whether we should have firstOrElse, lastOrElse, 
getAtOrElse, etc., it is certainly a possibility to add such a whole myriad of 
duplicated methods but there might be better alternatives. Does the existing 
ListWtihDefault work for you? It does mutate which might not be what you are 
after but perhaps we could create an alternative variant of that.

Cheers, Paul.


On Mon, Feb 18, 2019 at 7:36 AM Milles, Eric (TR Tech, Content & Ops) 
mailto:eric.mil...@thomsonreuters.com>> wrote:

When I first worked all this up my target was Groovy 2.4.  If that is raised to 
Groovy 2.5+ I just started to wonder if java.util.Optional could be leveraged 
for an improved solution.  I also remembered some feedback some time ago from 
MG where to no-arg call would be "getName()" so that it could be used in Groovy 
sources as "name".  Then if there were versions with more arguments, they would 
be "name(arg1, arg2, ...)".


So if I were to implement new DGMs in a vacuum, would something like this make 
sense?


public static  Optional getFirst(Iterable self)

public static  Optional getFirst(List self)

public static  Optional getFirst(T[] self)
public static  Optional getFirst(org.codehaus.groovy.runtime.NullObject 
self)

This could be used like "list.first.orElse(defaultValue)".  Now that I write 
that out, I can see the conflict with list spread shorthand.  Darn, I wish that 
didn't exist and you had to explicitly use "list*.prop".


General question: Are there limitations to using Java 8 stuff in Groovy core?  
I'm not sure how Android support comes into play here.



From: Milles, Eric (TR Tech, Content & Ops) 
mailto:eric.mil...@thomsonreuters.com>>
Sent: Sunday, February 17, 2019 1:56 PM
To: dev@groovy.apache.org<mailto:dev@groovy.apache.org>
Subject: Re: DGM for first or default


I'd like to restart this discussion.  I'm not sure if this should move to new 
JIRA ticket or Pull Request.  There are a few open questions I'd like to get 
some feedback on.  I have managed to solve the problem of getting from a null 
array/iterable.


My use case is getting the first item from an iterable or else a supplied 
default.  Alternate proposals like "list?.first() ?: defaultValue" or 
"list?.find() ?: defaultValue" do not properly handle all use cases.  It took 
quite a number of tries to figure it out.


"list ? list.first() : defaultValue" appears to be roughly equivalent.  
However, having the additional DGMs would mean a one-time check for non-null, 
non-empty and elimination of repeated "list", which may be a more complicated 
expression.  And in rare cases, a type could extend Iterable and provide a 
non-standard implementation of asBoolean().



Proposed additions to DefaultGroovyMethods:


public static  T firstOrElse(Iterable self, T defaultValue)

public static  T firstOrElse(List self, T defaultValue) // allows use of 
isEmpty() and get(i) instead of creating an Iterator instance

public static  T firstOrElse(T[] self, T defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, T 
defaultValue) // exists solely for the (null).firstOrDefault(value) case


public static  T firstOrElse(Iterable self, Supplier defaultValue)

public static  T firstOrElse(List self, Supplier defaultValue)

public static  T firstOrElse(T[] self, Supplier defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, 
Supplier defaultValue)

Since this is targeted at Groovy 2.5+ I have selected 
java.util.function.Supplier instead of groovy.lang.Closure.  Although that 
could be changed if a new Groovy 2.4 minor release was planned.


Usage:
  Iterable iterable = null
  println iterable.firstOrElse('default') // prints 'default'

  iterable = []
  println iterable.firstOrElse('default') // prints 'default'

  ite

Re: DGM for first or default

2019-02-17 Thread Paul King

Groovy 2.5 still has JDK 7 as minimum whereas Groovy 3.0 has 8 as minimum.
You can still add DGM methods
into org.codehaus.groovy.vmplugin.v8.PluginDefaultGroovyMethods and then
they will only be available when running on a JDK8+ VM.

Wrt to the question of whether we should have firstOrElse, lastOrElse,
getAtOrElse, etc., it is certainly a possibility to add such a whole myriad
of duplicated methods but there might be better alternatives. Does the
existing ListWtihDefault work for you? It does mutate which might not be
what you are after but perhaps we could create an alternative variant of
that.

Cheers, Paul.


On Mon, Feb 18, 2019 at 7:36 AM Milles, Eric (TR Tech, Content & Ops) <
eric.mil...@thomsonreuters.com> wrote:

> When I first worked all this up my target was Groovy 2.4.  If that is
> raised to Groovy 2.5+ I just started to wonder if java.util.Optional
> could be leveraged for an improved solution.  I also remembered some
> feedback some time ago from MG where to no-arg call would be "getName()" so
> that it could be used in Groovy sources as "name".  Then if there were
> versions with more arguments, they would be "name(arg1, arg2, ...)".
>
>
> So if I were to implement new DGMs in a vacuum, would something like this
> make sense?
>
>
> public static  Optional getFirst(Iterable self)
>
> public static  Optional getFirst(List self)
> public static  Optional getFirst(T[] self)
> public static  Optional getFirst(
> org.codehaus.groovy.runtime.NullObject self)
>
>
> This could be used like "list.first.orElse(defaultValue)".  Now that I
> write that out, I can see the conflict with list spread shorthand.  Darn, I
> wish that didn't exist and you had to explicitly use "list*.prop".
>
>
> *General question: *Are there limitations to using Java 8 stuff in Groovy
> core?  I'm not sure how Android support comes into play here.
>
>
> --
> *From:* Milles, Eric (TR Tech, Content & Ops) <
> eric.mil...@thomsonreuters.com>
> *Sent:* Sunday, February 17, 2019 1:56 PM
> *To:* dev@groovy.apache.org
> *Subject:* Re: DGM for first or default
>
>
> I'd like to restart this discussion.  I'm not sure if this should move to
> new JIRA ticket or Pull Request.  There are a few open questions I'd like
> to get some feedback on.  I have managed to solve the problem of getting
> from a null array/iterable.
>
>
> My use case is getting the first item from an iterable or else a supplied
> default.  Alternate proposals like "list?.first() ?: defaultValue" or
> "list?.find() ?: defaultValue" do not properly handle all use cases.  It
> took quite a number of tries to figure it out.
>
>
> "list ? list.first() : defaultValue" appears to be roughly equivalent.
> However, having the additional DGMs would mean a one-time check for
> non-null, non-empty and elimination of repeated "list", which may be a more
> complicated expression.  And in rare cases, a type could extend Iterable and
> provide a non-standard implementation of asBoolean().
>
>
>
> *Proposed additions to DefaultGroovyMethods:*
>
>
> public static  T firstOrElse(Iterable self, T defaultValue)
>
> public static  T firstOrElse(List self, T defaultValue) // allows
> use of isEmpty() and get(i) instead of creating an Iterator instance
>
> public static  T firstOrElse(T[] self, T defaultValue)
>
> public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject
> self, T defaultValue) // exists solely for the (null).firstOrDefault(value)
> case
>
> public static  T firstOrElse(Iterable self, Supplier defaultValue
> )
>
> public static  T firstOrElse(List self, Supplier defaultValue)
>
> public static  T firstOrElse(T[] self, Supplier defaultValue)
>
> public static  T
> firstOrElse(org.codehaus.groovy.runtime.NullObject self, Supplier
> defaultValue)
>
> Since this is targeted at Groovy 2.5+ I have selected
> java.util.function.Supplier instead of groovy.lang.Closure.  Although that
> could be changed if a new Groovy 2.4 minor release was planned.
>
>
> *Usage:*
>   Iterable iterable = null
>   println iterable.firstOrElse('default') // prints 'default'
>
>   iterable = []
>   println iterable.firstOrElse('default') // prints 'default'
>
>   iterable = [0]
>   println iterable.firstOrElse('default') // prints 0
>
>   iterable = [null]
>   println iterable.firstOrElse('default') // prints null
>
>   iterable = [false]
>   println iterable.firstOrElse('default') // prints false
>
>   iterable = null
>   iterable.firstOrElse { -> throw new ExceptionOfMyChoosing() } // throws
>
>
>
> *Open items:*
>
>
>

Re: DGM for first or default

2019-02-17 Thread Milles, Eric (TR Tech, Content & Ops)

When I first worked all this up my target was Groovy 2.4.  If that is raised to 
Groovy 2.5+ I just started to wonder if java.util.Optional could be leveraged 
for an improved solution.  I also remembered some feedback some time ago from 
MG where to no-arg call would be "getName()" so that it could be used in Groovy 
sources as "name".  Then if there were versions with more arguments, they would 
be "name(arg1, arg2, ...)".


So if I were to implement new DGMs in a vacuum, would something like this make 
sense?


public static  Optional getFirst(Iterable self)

public static  Optional getFirst(List self)

public static  Optional getFirst(T[] self)
public static  Optional getFirst(org.codehaus.groovy.runtime.NullObject 
self)

This could be used like "list.first.orElse(defaultValue)".  Now that I write 
that out, I can see the conflict with list spread shorthand.  Darn, I wish that 
didn't exist and you had to explicitly use "list*.prop".


General question: Are there limitations to using Java 8 stuff in Groovy core?  
I'm not sure how Android support comes into play here.



From: Milles, Eric (TR Tech, Content & Ops) 
Sent: Sunday, February 17, 2019 1:56 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default


I'd like to restart this discussion.  I'm not sure if this should move to new 
JIRA ticket or Pull Request.  There are a few open questions I'd like to get 
some feedback on.  I have managed to solve the problem of getting from a null 
array/iterable.


My use case is getting the first item from an iterable or else a supplied 
default.  Alternate proposals like "list?.first() ?: defaultValue" or 
"list?.find() ?: defaultValue" do not properly handle all use cases.  It took 
quite a number of tries to figure it out.


"list ? list.first() : defaultValue" appears to be roughly equivalent.  
However, having the additional DGMs would mean a one-time check for non-null, 
non-empty and elimination of repeated "list", which may be a more complicated 
expression.  And in rare cases, a type could extend Iterable and provide a 
non-standard implementation of asBoolean().



Proposed additions to DefaultGroovyMethods:


public static  T firstOrElse(Iterable self, T defaultValue)

public static  T firstOrElse(List self, T defaultValue) // allows use of 
isEmpty() and get(i) instead of creating an Iterator instance

public static  T firstOrElse(T[] self, T defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, T 
defaultValue) // exists solely for the (null).firstOrDefault(value) case


public static  T firstOrElse(Iterable self, Supplier defaultValue)

public static  T firstOrElse(List self, Supplier defaultValue)

public static  T firstOrElse(T[] self, Supplier defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, 
Supplier defaultValue)

Since this is targeted at Groovy 2.5+ I have selected 
java.util.function.Supplier instead of groovy.lang.Closure.  Although that 
could be changed if a new Groovy 2.4 minor release was planned.


Usage:
  Iterable iterable = null
  println iterable.firstOrElse('default') // prints 'default'

  iterable = []
  println iterable.firstOrElse('default') // prints 'default'

  iterable = [0]
  println iterable.firstOrElse('default') // prints 0

  iterable = [null]
  println iterable.firstOrElse('default') // prints null

  iterable = [false]
  println iterable.firstOrElse('default') // prints false

  iterable = null
  iterable.firstOrElse { -> throw new ExceptionOfMyChoosing() } // throws



Open items:


  1.  Should a set of methods "lastOrElse" also be created?  It would not take 
much effort to add them at the same time.
  2.  Should the "getAt" methods be similarly extended, like "public static  
T getAt(List self, int idx, T defaultValue)", etc.
  3.  If "getAt" is extended in this way, would it be useful to also consider 
extending the "[idx]" syntax form of "getAt" to include the default?
  4.  There was a question raised: if "iterable" contains Closures or 
Suppliers, how should that case be handled?  I'm curious how often this might 
come up.



____
From: Milles, Eric (TR Technology & Ops) 
Sent: Friday, October 19, 2018 10:54 AM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default


These may seem a bit simple for DGMs, but they do solve a couple problems as 
compared to "list ? list.first() ?: defaultValue".  First, no repetition of the 
"list" expression, which may be complex.  Second, content assist will show 
proposals for these methods.  Third, the Groovy truth problems with "list?[0] 
?: defaultValue", "list?.getAt(0) ?: defaultValue", "list.find() ?: 
defaultValue" and others do not e

Re: DGM for first or default

2019-02-17 Thread Milles, Eric (TR Tech, Content & Ops)

I'd like to restart this discussion.  I'm not sure if this should move to new 
JIRA ticket or Pull Request.  There are a few open questions I'd like to get 
some feedback on.  I have managed to solve the problem of getting from a null 
array/iterable.


My use case is getting the first item from an iterable or else a supplied 
default.  Alternate proposals like "list?.first() ?: defaultValue" or 
"list?.find() ?: defaultValue" do not properly handle all use cases.  It took 
quite a number of tries to figure it out.


"list ? list.first() : defaultValue" appears to be roughly equivalent.  
However, having the additional DGMs would mean a one-time check for non-null, 
non-empty and elimination of repeated "list", which may be a more complicated 
expression.  And in rare cases, a type could extend Iterable and provide a 
non-standard implementation of asBoolean().



Proposed additions to DefaultGroovyMethods:


public static  T firstOrElse(Iterable self, T defaultValue)

public static  T firstOrElse(List self, T defaultValue) // allows use of 
isEmpty() and get(i) instead of creating an Iterator instance

public static  T firstOrElse(T[] self, T defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, T 
defaultValue) // exists solely for the (null).firstOrDefault(value) case


public static  T firstOrElse(Iterable self, Supplier defaultValue)

public static  T firstOrElse(List self, Supplier defaultValue)

public static  T firstOrElse(T[] self, Supplier defaultValue)

public static  T firstOrElse(org.codehaus.groovy.runtime.NullObject self, 
Supplier defaultValue)

Since this is targeted at Groovy 2.5+ I have selected 
java.util.function.Supplier instead of groovy.lang.Closure.  Although that 
could be changed if a new Groovy 2.4 minor release was planned.


Usage:
  Iterable iterable = null
  println iterable.firstOrElse('default') // prints 'default'

  iterable = []
  println iterable.firstOrElse('default') // prints 'default'

  iterable = [0]
  println iterable.firstOrElse('default') // prints 0

  iterable = [null]
  println iterable.firstOrElse('default') // prints null

  iterable = [false]
  println iterable.firstOrElse('default') // prints false

  iterable = null
  iterable.firstOrElse { -> throw new ExceptionOfMyChoosing() } // throws



Open items:


  1.  Should a set of methods "lastOrElse" also be created?  It would not take 
much effort to add them at the same time.
  2.  Should the "getAt" methods be similarly extended, like "public static  
T getAt(List self, int idx, T defaultValue)", etc.
  3.  If "getAt" is extended in this way, would it be useful to also consider 
extending the "[idx]" syntax form of "getAt" to include the default?
  4.  There was a question raised: if "iterable" contains Closures or 
Suppliers, how should that case be handled?  I'm curious how often this might 
come up.




From: Milles, Eric (TR Technology & Ops) 
Sent: Friday, October 19, 2018 10:54 AM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default


These may seem a bit simple for DGMs, but they do solve a couple problems as 
compared to "list ? list.first() ?: defaultValue".  First, no repetition of the 
"list" expression, which may be complex.  Second, content assist will show 
proposals for these methods.  Third, the Groovy truth problems with "list?[0] 
?: defaultValue", "list?.getAt(0) ?: defaultValue", "list.find() ?: 
defaultValue" and others do not exist for these.  If the first element is null 
or otherwise falsy, it will be returned as desired.  The only case for me that 
is unresolved is a null array or iterable.  In this case, Groovy throws "Cannot 
invoke method firstOrElse() on null obect" instead of running the method 
allowing null tolerance and return of default value.


public static  T firstOrElse(Iterable self, T defaultValue) {
Iterator iter = self.iterator();
if (iter.hasNext()) {
return iter.next();
}
return defaultValue;
}
public static  T firstOrElse(T[] self, T defaultValue) {
if (self.length > 0) {
return self[0];
}
return defaultValue;
}
// and similarly for the Closure (or java.util.function.Supplier if Java 8+ 
only) variants


Since safe navigation is being explored for by-index access, is there a 
possibility for including some for of "or supplied default" in any of the 
safe-navigation cases?  I personally find the new safe-indexing syntax to be 
unnecessary when "list?.getAt(i)" appears to be the equivalent to "list?[i]".


Alternate proposal, what if the DGM.getAt(self, int idx) had variants that 
included a default value return instead of hard-coded null?  Like this:

public static

Re: DGM for first or default

2018-10-19 Thread Milles, Eric (TR Technology & Ops)

These may seem a bit simple for DGMs, but they do solve a couple problems as 
compared to "list ? list.first() ?: defaultValue".  First, no repetition of the 
"list" expression, which may be complex.  Second, content assist will show 
proposals for these methods.  Third, the Groovy truth problems with "list?[0] 
?: defaultValue", "list?.getAt(0) ?: defaultValue", "list.find() ?: 
defaultValue" and others do not exist for these.  If the first element is null 
or otherwise falsy, it will be returned as desired.  The only case for me that 
is unresolved is a null array or iterable.  In this case, Groovy throws "Cannot 
invoke method firstOrElse() on null obect" instead of running the method 
allowing null tolerance and return of default value.


public static  T firstOrElse(Iterable self, T defaultValue) {
Iterator iter = self.iterator();
if (iter.hasNext()) {
return iter.next();
}
return defaultValue;
}
public static  T firstOrElse(T[] self, T defaultValue) {
if (self.length > 0) {
return self[0];
}
return defaultValue;
}
// and similarly for the Closure (or java.util.function.Supplier if Java 8+ 
only) variants


Since safe navigation is being explored for by-index access, is there a 
possibility for including some for of "or supplied default" in any of the 
safe-navigation cases?  I personally find the new safe-indexing syntax to be 
unnecessary when "list?.getAt(i)" appears to be the equivalent to "list?[i]".


Alternate proposal, what if the DGM.getAt(self, int idx) had variants that 
included a default value return instead of hard-coded null?  Like this:

public static  T getAt(List self, int idx, T def) {
int size = self.size();
int i = normaliseIndex(idx, size);
if (i < size) {
return self.get(i);
} else {
//return null;
return def;
}
}




From: Mario Garcia 
Sent: Thursday, October 18, 2018 6:19 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default

Good point OC:

[0,'',[],[:]].find()?:'not quite what you wanted here'
[0,1,2].find()?:'nor in this case'

The more I think on this the more I think is an interesting topic. I fully 
understand your frustration with first(), but apart from the example with Cocoa 
you mentioned, looking in the JVM it turns out there're plenty of examples of 
language collections behaving that way:

In scala the head of an empty list does throw an exception
---
scala> var empty = List[Int]()
empty: List[Int] = List()

scala> empty.head
java.util.NoSuchElementException: head of empty list
  at scala.collection.immutable.Nil$.head(List.scala:426)
  at scala.collection.immutable.Nil$.head(List.scala:423)
  ... 28 elided

scala>
-

and so does kotlin when calling to first()
--
Welcome to Kotlin version 1.2.71 (JRE 1.8.0_171-b11)
Type :help for help, :quit for quit
>>> val num: List = listOf()
>>> num.first()
java.util.NoSuchElementException: List is empty.
at kotlin.collections.CollectionsKt___CollectionsKt.first(_Collections.kt:184)
>>>
-
in Kotlin they have firstOrNull(), but I haven't found any overloaded function 
with a default value. They also have "find", but it's not possible to call it 
without parameter

However Clojure returns null whether:

  *   The first element was nil
  *   The list was empty
  *   Or the list was nil


user=> (def a nil)
#'user/a
user=> a
nil
user=> (first a)
nil
user=> (def a '(nil))
#'user/a
user=> a
(nil)
user=> (first a)
nil
user=> (def a '())
#'user/a
user=> a
()
user=> (first a)
nil
user=>
---

BTW I forgot to mention that Groovy 3 will have safe indexing meaning an 
expression like the following:

  *   will return the first element of a non empty list which I guess it will 
be the Kotlin firstOrNull() equivalent
  *   or null if the list was null or empty

-
// trying to get first element from null list
nullList?[0] ==> null

// trying to get an inexistent element from a non empty list (but this is not 
new, this is how a non empty list indexing works in Groovy)
nonNullList?[] => null
--

Outside the JVM, Haskell, when asking for the head of an empty list, throws an 
exception (There is an explanation in stackoverflow which I'm afraid I don't 
understand). So in the end Groovy's first() seems not to be the exception among 
other modern languages out there.

Another point of view, could be thinking about returning null consistently. 
Lets say a list returns null using first():

  *   Does it mean the first element is a null value or is an empty list and 
that's why is giving me a null value ?
  *   What if

Re: DGM for first or default

2018-10-18 Thread Mario Garcia

Good point OC:

[0,'',[],[:]].find()?:'not quite what you wanted here'
[0,1,2].find()?:'nor in this case'

The more I think on this the more I think is an interesting topic. I fully
understand your frustration with first(), but apart from the example with
Cocoa you mentioned, looking in the JVM it turns out there're plenty of
examples of language collections behaving that way:

In scala the head of an empty list does throw an exception
---
scala> var empty = List[Int]()
empty: List[Int] = List()

scala> empty.head
java.util.NoSuchElementException: head of empty list
  at scala.collection.immutable.Nil$.head(List.scala:426)
  at scala.collection.immutable.Nil$.head(List.scala:423)
  ... 28 elided

scala>
-

and so does kotlin when calling to first()
--
Welcome to Kotlin version 1.2.71 (JRE 1.8.0_171-b11)
Type :help for help, :quit for quit
>>> val num: List = listOf()
>>> num.first()
java.util.NoSuchElementException: List is empty.
at
kotlin.collections.CollectionsKt___CollectionsKt.first(_Collections.kt:184)
>>>
-
in Kotlin they have firstOrNull(), but I haven't found any overloaded
function with a default value. They also have "find", but it's not possible
to call it without parameter

However Clojure returns null whether:

   - The first element was nil
   - The list was empty
   - Or the list was nil

user=> (def a nil)
#'user/a
user=> a
nil
user=> (first a)
nil
user=> (def a '(nil))
#'user/a
user=> a
(nil)
user=> (first a)
nil
user=> (def a '())
#'user/a
user=> a
()
user=> (first a)
nil
user=>
---

BTW I forgot to mention that Groovy 3 will have safe indexing meaning an
expression like the following:

   - will return the first element of a non empty list which I guess it
   will be the Kotlin firstOrNull() equivalent
   - or null if the list was null or empty

-
// trying to get first element from null list
nullList?[0] ==> null

// trying to get an inexistent element from a non empty list (but this is
not new, this is how a non empty list indexing works in Groovy)
nonNullList?[] => null
--

Outside the JVM, Haskell, when asking for the head of an empty list, throws
an exception (There is an explanation in stackoverflow which I'm afraid I
don't understand). So in the end Groovy's first() seems not to be the
exception among other modern languages out there.

Another point of view, could be thinking about returning null consistently.
Lets say a list returns null using first():

   - Does it mean the first element is a null value or is an empty list and
   that's why is giving me a null value ?
   - What if null is a valid value, with some meaning in my process ? With
   that context a method like firstOrNull() (even first(defaultValue) with a
   null list) could be considered ambiguous.

My guess is that in the case of languages throwing an exception using
first() on an empty list, when they designed the language collections they
didn't have any other way to express that kind of semantics. But this is
just a lucky guess. I'm probably wrong. I only can think of pattern
matching as a complete solution, where the terminal result in the case of
an empty or null list, is a default value different than any of the
elements of the expected result set ?

I apologize in advance for the lengthy e-mail, but it seemed interesting to
think why first() was designed like that, not only in Groovy, but in some
other languages as well.
Mario

El jue., 18 oct. 2018 a las 20:27, Milles, Eric (TR Technology & Ops) (<
eric.mil...@thomsonreuters.com>) escribió:

> I think first() exists so there is a semantic pair for functional
> programming: first()/head() and tail()  or init() and last()
>
> --
> *From:* ocs@ocs 
> *Sent:* Thursday, October 18, 2018 1:20 PM
> *To:* dev@groovy.apache.org
> *Subject:* Re: DGM for first or default
>
> Well I thought *first* is smart enough to return *null* for an empty
> list, same as my *firstObject* in Cocoa does. If it throws, what's on
> earth point of having the thing at all? In that case it can be replaced by
> *list[0]* without any drawback at all.
>
> All the best,
> OC
>
> On 18 Oct 2018, at 7:19 PM, Milles, Eric (TR Technology & Ops) <
> eric.mil...@thomsonreuters.com> wrote:
>
> "list?.first() ?: defaultValue" is not the equivalent.  If the collection
> is empty, first() throws an IndexOutOfBoundsException is thrown.  That's
> why I'm asking if there is a simple equivalent.  I suppose this is the
> equivalent now that I think about it:
>
> list ? list.first() : defaultValue
>
>
> --
> *From:* ocs@ocs 
> *Sent:* Thursday, October 18, 2018 12:07 PM
> *To:* dev@groovy.apache.org
> *Subje

Re: DGM for first or default

2018-10-18 Thread Milles, Eric (TR Technology & Ops)

I think first() exists so there is a semantic pair for functional programming: 
first()/head() and tail()  or init() and last()

From: ocs@ocs 
Sent: Thursday, October 18, 2018 1:20 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default

Well I thought first is smart enough to return null for an empty list, same as 
my firstObject in Cocoa does. If it throws, what's on earth point of having the 
thing at all? In that case it can be replaced by list[0] without any drawback 
at all.

All the best,
OC

On 18 Oct 2018, at 7:19 PM, Milles, Eric (TR Technology & Ops) 
mailto:eric.mil...@thomsonreuters.com>> wrote:

"list?.first() ?: defaultValue" is not the equivalent.  If the collection is 
empty, first() throws an IndexOutOfBoundsException is thrown.  That's why I'm 
asking if there is a simple equivalent.  I suppose this is the equivalent now 
that I think about it:

list ? list.first() : defaultValue

From: ocs@ocs mailto:o...@ocs.cz>>
Sent: Thursday, October 18, 2018 12:07 PM
To: dev@groovy.apache.org<mailto:dev@groovy.apache.org>
Subject: Re: DGM for first or default

Myself, I am not a huge fan of adding not-often-needed functionalities (and 
actually would add almost none of those discussed lately); nevertheless...

On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso 
mailto:paolo.ditomm...@gmail.com>> wrote:

-1, it can be easily done as:
list.first() ?: defaultValue

... this won't work in case the first object is a Groovy False (e.g., an empty 
string, or a plethora of others).

All the best,
OC

p

On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun 
mailto:sun...@apache.org>> wrote:
+0 from me.
P.S. we should add similar DGM for `last` too?

Cheers,
Daniel.Sun

-
Daniel Sun
Apache Groovy committer
Blog: 
http://blog.sunlan.me<https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
Twitter: @daniel_sun

--
Sent from: 
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Re: DGM for first or default

2018-10-18 Thread ocs@ocs

[0,'',[],[:]].find()?:'not quite what you wanted here'
[0,1,2].find()?:'nor in this case'

Actually, far as my experience can say, there's precisely one reason to have 
first/last, and that is that they won't throw, but return a null on an empty 
list. If they do not, there's no point in having those at all, for indices can 
be used instead just as well.

All the best,
OC

> On 18 Oct 2018, at 7:52 PM, Mario Garcia  wrote:
> 
> Eric you can use `find`:
> 
> list.find() ?: defaultValue
> 
> The method find with no arguments takes the first element, and if the 
> collection is empty or null it will return null and you won't get an 
> IndexOutOfBounds
> 
> Regards
> Mario
> 
> El jue., 18 oct. 2018 a las 19:32, Milles, Eric (TR Technology & Ops) 
> (mailto:eric.mil...@thomsonreuters.com>>) 
> escribió:
> Is it still valuable to have DGMs -- whether named "first()" or 
> "firstOrDefault()" or whatever?  Content assist does not propose "list ? 
> list.first() : defaultValue".  I suppose I'd need to create a code template 
> to get that proposal in the IDE.
> 
> Are there any other small idioms like this that anyone has added as a 
> template to improve the editing experience?
> From: Milles, Eric (TR Technology & Ops)
> Sent: Thursday, October 18, 2018 12:19:42 PM
> To: dev@groovy.apache.org <mailto:dev@groovy.apache.org>
> Subject: Re: DGM for first or default
>  
> "list?.first() ?: defaultValue" is not the equivalent.  If the collection is 
> empty, first() throws an IndexOutOfBoundsException is thrown.  That's why I'm 
> asking if there is a simple equivalent.  I suppose this is the equivalent now 
> that I think about it:
> 
> list ? list.first() : defaultValue
> 
> 
> From: ocs@ocs mailto:o...@ocs.cz>>
> Sent: Thursday, October 18, 2018 12:07 PM
> To: dev@groovy.apache.org <mailto:dev@groovy.apache.org>
> Subject: Re: DGM for first or default
>  
> Myself, I am not a huge fan of adding not-often-needed functionalities (and 
> actually would add almost none of those discussed lately); nevertheless...
> 
>> On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso > <mailto:paolo.ditomm...@gmail.com>> wrote:
>> 
>> -1, it can be easily done as: 
>> list.first() ?: defaultValue
> 
> ... this won't work in case the first object is a Groovy False (e.g., an 
> empty string, or a plethora of others).
> 
> All the best,
> OC
> 
>> 
>> 
>> p
>> 
>> On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun > <mailto:sun...@apache.org>> wrote:
>> +0 from me.
>> P.S. we should add similar DGM for `last` too?
>> 
>> Cheers,
>> Daniel.Sun
>> 
>> 
>> 
>> 
>> -
>> Daniel Sun 
>> Apache Groovy committer 
>> Blog: http://blog.sunlan.me 
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
>>  
>> Twitter: @daniel_sun 
>> 
>> --
>> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html 
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__groovy.329449.n5.nabble.com_Groovy-2DDev-2Df372993.html=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=J5vmRmzvL66tJOtxSbSidNjQHcCHKNV3t2A0OHPCgDY=>
>

Re: DGM for first or default

2018-10-18 Thread ocs@ocs

Well I thought first is smart enough to return null for an empty list, same as 
my firstObject in Cocoa does. If it throws, what's on earth point of having the 
thing at all? In that case it can be replaced by list[0] without any drawback 
at all.

All the best,
OC

> On 18 Oct 2018, at 7:19 PM, Milles, Eric (TR Technology & Ops) 
>  wrote:
> 
> "list?.first() ?: defaultValue" is not the equivalent.  If the collection is 
> empty, first() throws an IndexOutOfBoundsException is thrown.  That's why I'm 
> asking if there is a simple equivalent.  I suppose this is the equivalent now 
> that I think about it:
> 
> list ? list.first() : defaultValue
> 
> 
> From: ocs@ocs mailto:o...@ocs.cz>>
> Sent: Thursday, October 18, 2018 12:07 PM
> To: dev@groovy.apache.org <mailto:dev@groovy.apache.org>
> Subject: Re: DGM for first or default
>  
> Myself, I am not a huge fan of adding not-often-needed functionalities (and 
> actually would add almost none of those discussed lately); nevertheless...
> 
>> On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso > <mailto:paolo.ditomm...@gmail.com>> wrote:
>> 
>> -1, it can be easily done as: 
>> list.first() ?: defaultValue
> 
> ... this won't work in case the first object is a Groovy False (e.g., an 
> empty string, or a plethora of others).
> 
> All the best,
> OC
> 
>> 
>> 
>> p
>> 
>> On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun > <mailto:sun...@apache.org>> wrote:
>> +0 from me.
>> P.S. we should add similar DGM for `last` too?
>> 
>> Cheers,
>> Daniel.Sun
>> 
>> 
>> 
>> 
>> -
>> Daniel Sun 
>> Apache Groovy committer 
>> Blog: http://blog.sunlan.me 
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
>>  
>> Twitter: @daniel_sun 
>> 
>> --
>> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html 
>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__groovy.329449.n5.nabble.com_Groovy-2DDev-2Df372993.html=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=J5vmRmzvL66tJOtxSbSidNjQHcCHKNV3t2A0OHPCgDY=>

Re: DGM for first or default

2018-10-18 Thread Mario Garcia

Eric you can use `find`:

list.find() ?: defaultValue

The method find with no arguments takes the first element, and if the
collection is empty or null it will return null and you won't get an
IndexOutOfBounds

Regards
Mario

El jue., 18 oct. 2018 a las 19:32, Milles, Eric (TR Technology & Ops) (<
eric.mil...@thomsonreuters.com>) escribió:

> Is it still valuable to have DGMs -- whether named "first()" or
> "firstOrDefault()" or whatever?  Content assist does not propose "list ?
> list.first() : defaultValue".  I suppose I'd need to create a code template
> to get that proposal in the IDE.
>
>
> Are there any other small idioms like this that anyone has added as a
> template to improve the editing experience?
> --
> *From:* Milles, Eric (TR Technology & Ops)
> *Sent:* Thursday, October 18, 2018 12:19:42 PM
> *To:* dev@groovy.apache.org
> *Subject:* Re: DGM for first or default
>
>
> "list?.first() ?: defaultValue" is not the equivalent.  If the collection
> is empty, first() throws an IndexOutOfBoundsException is thrown.  That's
> why I'm asking if there is a simple equivalent.  I suppose this is the
> equivalent now that I think about it:
>
>
> list ? list.first() : defaultValue
>
>
> --------------
> *From:* ocs@ocs 
> *Sent:* Thursday, October 18, 2018 12:07 PM
> *To:* dev@groovy.apache.org
> *Subject:* Re: DGM for first or default
>
> Myself, I am not a huge fan of adding not-often-needed functionalities
> (and actually would add almost none of those discussed lately);
> nevertheless...
>
> On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso 
> wrote:
>
> -1, it can be easily done as:
> list.first() ?: defaultValue
>
>
> ... this won't work in case the first object is a Groovy False (e.g., an
> empty string, or a plethora of others).
>
> All the best,
> OC
>
>
>
> p
>
> On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun  wrote:
>
> +0 from me.
> P.S. we should add similar DGM for `last` too?
>
> Cheers,
> Daniel.Sun
>
>
>
>
> -
> Daniel Sun
> Apache Groovy committer
> Blog: http://blog.sunlan.me
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
> Twitter: @daniel_sun
>
> --
> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__groovy.329449.n5.nabble.com_Groovy-2DDev-2Df372993.html=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=J5vmRmzvL66tJOtxSbSidNjQHcCHKNV3t2A0OHPCgDY=>
>
>
>

Re: DGM for first or default

2018-10-18 Thread Milles, Eric (TR Technology & Ops)

Is it still valuable to have DGMs -- whether named "first()" or 
"firstOrDefault()" or whatever?  Content assist does not propose "list ? 
list.first() : defaultValue".  I suppose I'd need to create a code template to 
get that proposal in the IDE.


Are there any other small idioms like this that anyone has added as a template 
to improve the editing experience?


From: Milles, Eric (TR Technology & Ops)
Sent: Thursday, October 18, 2018 12:19:42 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default


"list?.first() ?: defaultValue" is not the equivalent.  If the collection is 
empty, first() throws an IndexOutOfBoundsException is thrown.  That's why I'm 
asking if there is a simple equivalent.  I suppose this is the equivalent now 
that I think about it:


list ? list.first() : defaultValue



From: ocs@ocs 
Sent: Thursday, October 18, 2018 12:07 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default

Myself, I am not a huge fan of adding not-often-needed functionalities (and 
actually would add almost none of those discussed lately); nevertheless...

On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso 
mailto:paolo.ditomm...@gmail.com>> wrote:

-1, it can be easily done as:
list.first() ?: defaultValue

... this won't work in case the first object is a Groovy False (e.g., an empty 
string, or a plethora of others).

All the best,
OC



p

On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun 
mailto:sun...@apache.org>> wrote:
+0 from me.
P.S. we should add similar DGM for `last` too?

Cheers,
Daniel.Sun




-
Daniel Sun
Apache Groovy committer
Blog: 
http://blog.sunlan.me<https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
Twitter: @daniel_sun

--
Sent from: 
http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__groovy.329449.n5.nabble.com_Groovy-2DDev-2Df372993.html=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=J5vmRmzvL66tJOtxSbSidNjQHcCHKNV3t2A0OHPCgDY=>

Re: DGM for first or default

2018-10-18 Thread Milles, Eric (TR Technology & Ops)

"list?.first() ?: defaultValue" is not the equivalent.  If the collection is 
empty, first() throws an IndexOutOfBoundsException is thrown.  That's why I'm 
asking if there is a simple equivalent.  I suppose this is the equivalent now 
that I think about it:


list ? list.first() : defaultValue



From: ocs@ocs 
Sent: Thursday, October 18, 2018 12:07 PM
To: dev@groovy.apache.org
Subject: Re: DGM for first or default

Myself, I am not a huge fan of adding not-often-needed functionalities (and 
actually would add almost none of those discussed lately); nevertheless...

On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso 
mailto:paolo.ditomm...@gmail.com>> wrote:

-1, it can be easily done as:
list.first() ?: defaultValue

... this won't work in case the first object is a Groovy False (e.g., an empty 
string, or a plethora of others).

All the best,
OC



p

On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun 
mailto:sun...@apache.org>> wrote:
+0 from me.
P.S. we should add similar DGM for `last` too?

Cheers,
Daniel.Sun




-
Daniel Sun
Apache Groovy committer
Blog: 
http://blog.sunlan.me<https://urldefense.proofpoint.com/v2/url?u=http-3A__blog.sunlan.me_=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=Kuqjwc4Pu38Y9C4Zooo3uBjDkGvyna3lloonS2m7GTE=>
Twitter: @daniel_sun

--
Sent from: 
http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__groovy.329449.n5.nabble.com_Groovy-2DDev-2Df372993.html=DwMFAg=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww=eCM29fHJoKqW_CdKJO2GxdVR6VMqldnDZ9NQgYxSo08=J5vmRmzvL66tJOtxSbSidNjQHcCHKNV3t2A0OHPCgDY=>

Re: DGM for first or default

2018-10-18 Thread Paolo Di Tommaso

ouch.. true! if so:

list ? list.first() : defaultValue


p








On Thu, Oct 18, 2018 at 7:07 PM ocs@ocs  wrote:

> Myself, I am not a huge fan of adding not-often-needed functionalities
> (and actually would add almost none of those discussed lately);
> nevertheless...
>
> On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso 
> wrote:
>
> -1, it can be easily done as:
> list.first() ?: defaultValue
>
>
> ... this won't work in case the first object is a Groovy False (e.g., an
> empty string, or a plethora of others).
>
> All the best,
> OC
>
>
>
> p
>
> On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun  wrote:
>
>> +0 from me.
>> P.S. we should add similar DGM for `last` too?
>>
>> Cheers,
>> Daniel.Sun
>>
>>
>>
>>
>> -
>> Daniel Sun
>> Apache Groovy committer
>> Blog: http://blog.sunlan.me
>> Twitter: @daniel_sun
>>
>> --
>> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html
>>
>
>

Re: DGM for first or default

2018-10-18 Thread ocs@ocs

P.S. Oh, and when I am writing anyway — please, do not abuse the “overloaded” 
methods which differ just by their argument lists (myself, I consider them 
always at best suspicious; mostly plain wrong). Instead of the suggestion 
below, if something like that is accepted, it would be much better to change 
the method name appropriately (say, e.g., firstWithDefault, firstWithSupplier). 
Or perhaps named arguments might be (consistently!) used for these things 
(e.g., “first(default:value)” or “first(supplier:value)”).

Consider e.g., an array of closures, of which one would want to get the first 
one with a default closure... with the definitions suggested below that's going 
to be fun!

All the best,
OC

> On 18 Oct 2018, at 5:39 PM, Milles, Eric (TR Technology & Ops) 
>  wrote:
> 
> I see there are the following DGMs for getting first element of a 
> "collection":
>   static  T first(T[] self)
>   static  T first(List self)
>   static  T first(Iterable self)
> 
> Is there a simple sequence for getting the first element or a default value 
> if the "collection" is empty?  If not, may I propose the addition of the 
> following DGMs:
>   static  T first(T[] self, T defaultValue)
>   static  T first(List self, T defaultValue)
>   static  T first(Iterable self, T defaultValue)
>   static  T first(T[] self, Closure defaultSupplier)
>   static  T first(List self, Closure defaultSupplier)
>   static  T first(Iterable self, Closure defaultSupplier)
> 
> 
> Eric M.

Re: DGM for first or default

2018-10-18 Thread ocs@ocs

Myself, I am not a huge fan of adding not-often-needed functionalities (and 
actually would add almost none of those discussed lately); nevertheless...

> On 18 Oct 2018, at 6:48 PM, Paolo Di Tommaso  
> wrote:
> 
> -1, it can be easily done as: 
> list.first() ?: defaultValue

... this won't work in case the first object is a Groovy False (e.g., an empty 
string, or a plethora of others).

All the best,
OC

> 
> 
> p
> 
> On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun  > wrote:
> +0 from me.
> P.S. we should add similar DGM for `last` too?
> 
> Cheers,
> Daniel.Sun
> 
> 
> 
> 
> -
> Daniel Sun 
> Apache Groovy committer 
> Blog: http://blog.sunlan.me  
> Twitter: @daniel_sun 
> 
> --
> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html 
>

Re: DGM for first or default

2018-10-18 Thread Mauro Molinari


Isn't it equivalent to something like this?

|def elem = collection?.first()?: defaultValue||
||def elem = collection?.first()?: defaultSupplier()||
|
Mauro

Il 18/10/2018 17:39, Milles, Eric (TR Technology & Ops) ha scritto:


I see there are the following DGMs for getting first element of 
a "collection":


  staticTfirst(T[] self)

  staticTfirst(Listself)

staticTfirst(Iterableself)


*Is there a simple sequence for getting the first element or a default 
value if the "collection" is empty?*  If not, may I propose the 
addition of the following DGMs:


  staticTfirst(T[] self, TdefaultValue)

  staticTfirst(Listself, TdefaultValue)

  staticTfirst(Iterableself, TdefaultValue)

  staticTfirst(T[] self, Closure defaultSupplier)
staticTfirst(Listself, Closure defaultSupplier)

  staticTfirst(Iterableself, Closure defaultSupplier)



Eric M.

Re: DGM for first or default

2018-10-18 Thread Paolo Di Tommaso

-1, it can be easily done as:

list.first() ?: defaultValue


p

On Thu, Oct 18, 2018 at 6:45 PM Daniel.Sun  wrote:

> +0 from me.
> P.S. we should add similar DGM for `last` too?
>
> Cheers,
> Daniel.Sun
>
>
>
>
> -
> Daniel Sun
> Apache Groovy committer
> Blog: http://blog.sunlan.me
> Twitter: @daniel_sun
>
> --
> Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html
>

Re: DGM for first or default

2018-10-18 Thread Daniel.Sun

+0 from me.
P.S. we should add similar DGM for `last` too?

Cheers,
Daniel.Sun




-
Daniel Sun 
Apache Groovy committer 
Blog: http://blog.sunlan.me 
Twitter: @daniel_sun 

--
Sent from: http://groovy.329449.n5.nabble.com/Groovy-Dev-f372993.html

Re: DGM for first or default

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Re: DGM for first or default

Re: DGM for first or default

Re: DGM for first or default

Re: DGM for first or default

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Re: DGM for first or default

Re: DGM for first or default

Re: DGM for first or default

Re: DGM for first or default

Re: DGM for first or default

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