[jira] [Updated] (GROOVY-10943) Consider additional use of _ as a placeholder

["Paul King (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/GROOVY-10943?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paul King updated GROOVY-10943:
-------------------------------
    Description: 
Recent Java versions make underscore, "_", an illegal variable name. This is to allow it to be used as a placeholder as per JEP 302: Lambda Leftovers[1]. This issue is to explore how better to have such a placeholder in Groovy.

This strengthens an informal convention already in use. Instead of writing this:

{code}
def (coordX, coordY, unusedZ) = coord3D()
{code}

Sometimes it is written as:

{code}
def (coordX, coordY, _) = coord3D()
{code}

Currently, the underscore is a variable and could be used but the convention is that
it would be ignored.

This convention doesn't scale if more than one result is to be ignored (here a double underscore is used for the second ignored result):

{code}
def (coordX, coordY, _, __) = coord3DwithColor()
{code}

This idea being that the following should be valid:

{code}
def (coordX, coordY, _, _) = coord3DwithColor()
{code}

Which currently gives an error for the duplicated variable name.

Similarly, the idea is applicable for lambda parameters (as per the example in the previously mentioned Java JEP):
{code}
BiFunction<Integer, String, String> biss = (i, _) -> String.valueOf(i)
{code}

 [1] [https://openjdk.org/jeps/302]

 

  was:
Recent Java versions make underscore, "_", an illegal variable name. This is to allow it to be used as a placeholder as per JEP 302: Lambda Leftovers[1]. This issue is to explore how better to have such a placeholder in Groovy.

This strengthens an informal convention already in use. Instead of writing this:

{code}
def (coordX, coordY, unusedZ) = coord3D()
{code}

Sometimes it is written as:

{code}
def (coordX, coordY, _) = coord3D()
{code}


 [1] [https://openjdk.org/jeps/302]

 


> Consider additional use of _ as a placeholder
> ---------------------------------------------
>
>                 Key: GROOVY-10943
>                 URL: https://issues.apache.org/jira/browse/GROOVY-10943
>             Project: Groovy
>          Issue Type: Dependency upgrade
>            Reporter: Paul King
>            Priority: Major
>
> Recent Java versions make underscore, "_", an illegal variable name. This is to allow it to be used as a placeholder as per JEP 302: Lambda Leftovers[1]. This issue is to explore how better to have such a placeholder in Groovy.
> This strengthens an informal convention already in use. Instead of writing this:
> {code}
> def (coordX, coordY, unusedZ) = coord3D()
> {code}
> Sometimes it is written as:
> {code}
> def (coordX, coordY, _) = coord3D()
> {code}
> Currently, the underscore is a variable and could be used but the convention is that
> it would be ignored.
> This convention doesn't scale if more than one result is to be ignored (here a double underscore is used for the second ignored result):
> {code}
> def (coordX, coordY, _, __) = coord3DwithColor()
> {code}
> This idea being that the following should be valid:
> {code}
> def (coordX, coordY, _, _) = coord3DwithColor()
> {code}
> Which currently gives an error for the duplicated variable name.
> Similarly, the idea is applicable for lambda parameters (as per the example in the previously mentioned Java JEP):
> {code}
> BiFunction<Integer, String, String> biss = (i, _) -> String.valueOf(i)
> {code}
>  [1] [https://openjdk.org/jeps/302]
>  



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