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From "Matthias Boehm (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SYSTEMML-2078) Support for global constants
Date Sun, 11 Mar 2018 03:32:00 GMT

    [ https://issues.apache.org/jira/browse/SYSTEMML-2078?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16394389#comment-16394389
] 

Matthias Boehm commented on SYSTEMML-2078:
------------------------------------------

thanks for asking [~Guobao] - I would prefer not to introduce a stateful builtin function
like that because it would be very hard to properly integrate it for the general case. For
example, what are the semantics if this builtin function is called out of {{parfor}} iterations?

Instead, this task captures two much simpler aspects: 
1) The support for predefined constants such as NaN, and INF, which people currently have
to write as 0.0/0.0 and 1.0/0.0, respectively. Providing the builtin constants just makes
several scripts more readable and less error prone.
2) A changed scoping semantics, where the parent environment (including live variables) is
visible (but cannot be modified) in called functions even though these variables are not explicitly
passed. This would be consistent with R and would also allow simple global constant (simply
assign in the main script or some function and these variables become globally available).
 

> Support for global constants
> ----------------------------
>
>                 Key: SYSTEMML-2078
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-2078
>             Project: SystemML
>          Issue Type: Sub-task
>            Reporter: Matthias Boehm
>            Priority: Major
>
> Similar to R, where variables of the surrounding context are accessible, this task aims
to introduce global constant variables. Furthermore, we should also add builtin constants
such as NaN, INF, and PI.



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