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https://issues.apache.org/jira/browse/FREEMARKER-77?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16198539#comment-16198539
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Daniel Dekany commented on FREEMARKER-77:
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Or rather, first I want a concrete working solution in FM3, and then see how to
port ideas back without causing the least confusion...
The problem with `(...)!default` in FM2 is that parentheses already have a
commonly understood meaning. In particular, if the evaluation order with and
without the parenthesis is the same, like in the case of `(a * b) + c`, t can
be removed. `(...)!default` works differently, which is confusing. Can you show
me an example where you suspect the FM3 approach won't work well?
> expr!! as a shorthand for (expr)!
> ---------------------------------
>
> Key: FREEMARKER-77
> URL: https://issues.apache.org/jira/browse/FREEMARKER-77
> Project: Apache Freemarker
> Issue Type: New Feature
> Reporter: Ondra Žižka
> Priority: Minor
>
> a.very.long.expr!! could be a shorthand for {{(a.very.long.expr)!}}.
> The effect of !! would go back to the "root" of the expression, i.e. at the
> start of the part ending with !! . Not sure if that would have clear enough
> rules, though.
> The use case is, that often there is a long expression, (again, getting
> something from a deep graph), and anywhere on the path something can be
> missing. The only relevant thing is at the end. And the parentheses make the
> expression less readable.
> Example made-up situatuon:
> {code}
> (foo.bar.baz[(foo.transform((a.very.long.expression())!"defaultResult"))!fallbackKey(context)])!"-"
> {code}
> 1) The long expression can be missing at any point, so the transform would
> get some default value.
> 2) The transform may return null if the argument is somehow improper. For
> that case, the {{fallbackKey()}} would return a key as per the {{context}}.
> 3) If the map doesn't contain the entry or any of {{foo.bar.baz}} is missing,
> the whole expression would turn into {{"-"}}.
> {code}
> foo.bar.baz[foo.transform(a.very.long.expression()!!"defaultResult")!!fallbackKey(context)]!!"-"
> {code}
> Ok, this one is perhaps a candidate for splitting into few steps. But it's
> just for illustration.
> Does it make sense? Is it doable?
> Marking it as minor as it's not really too much pain, just would be nice to
> have.
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