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From "Henri Biestro (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (JEXL-114) Allow scripts to create local variables // Add return keyword
Date Mon, 11 Jul 2011 21:12:00 GMT

     [ https://issues.apache.org/jira/browse/JEXL-114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Henri Biestro updated JEXL-114:
-------------------------------

    Description: 
WHY:
Not having local variables nor return in scripts is inconvenient, especially when dealing
with loops.
This also precludes using read-only contexts easily which are really convenient when letting
end-users enter their own expressions.

HOW:
This could (will) be implemented by extending the parameters feature (script accept parameters
during parsing and thus arguments during evaluation) which is itself based on the notion of
'registers' - an array of objects that the interpreter allocates and uses based on script
information.
It only requires adding one keyword ("var" seems the obvious choice) in the .jjt.
The "return" keyword is also an easy .jjt addition; obvious implementation is to use an internal
exception to force traversing the stack up.

WHAT:
Add the "var" and "return" keyword.
Also add methods to extract the variables (global - see JEXL-113), the parameters (used during
parsing) and the local variables (declared within) a script to help pinpoint problems or prepare
the evaluation of scripts.



  was:
Not having local variables in scripts is inconvenient, especially when dealing with loops.
This also precludes using read-only contexts easily which are really convenient when letting
end-users enter their own expressions.

This could (will) be implemented by extending the parameters feature (script accept parameters
during parsing and thus arguments during evaluation) which is itself based on the notion of
'registers' - an array of objects that the interpreter allocates and uses based on script
information.

        Summary: Allow scripts to create local variables // Add return keyword  (was: Allow
scripts to create local variables)

> Allow scripts to create local variables // Add return keyword
> -------------------------------------------------------------
>
>                 Key: JEXL-114
>                 URL: https://issues.apache.org/jira/browse/JEXL-114
>             Project: Commons JEXL
>          Issue Type: Improvement
>    Affects Versions: 2.0.1
>            Reporter: Henri Biestro
>            Assignee: Henri Biestro
>             Fix For: 2.0.2
>
>
> WHY:
> Not having local variables nor return in scripts is inconvenient, especially when dealing
with loops.
> This also precludes using read-only contexts easily which are really convenient when
letting end-users enter their own expressions.
> HOW:
> This could (will) be implemented by extending the parameters feature (script accept parameters
during parsing and thus arguments during evaluation) which is itself based on the notion of
'registers' - an array of objects that the interpreter allocates and uses based on script
information.
> It only requires adding one keyword ("var" seems the obvious choice) in the .jjt.
> The "return" keyword is also an easy .jjt addition; obvious implementation is to use
an internal exception to force traversing the stack up.
> WHAT:
> Add the "var" and "return" keyword.
> Also add methods to extract the variables (global - see JEXL-113), the parameters (used
during parsing) and the local variables (declared within) a script to help pinpoint problems
or prepare the evaluation of scripts.

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