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