On Thu, Sep 24, 2009 at 14:22, Eelco Dolstra <e.dols...@tudelft.nl> wrote:
> Hi,
>
> Nicolas Pierron wrote:
>
>>> The "or" syntax seems a bit too different from the other part of the
>>> language and can be confused with a logical operator from other
>>> languages.
>
> Yes, but it has the advantages of not being an operator (which are never
> really
> intuitive, unless they're basic mathematical operators) and being very short.
>
>>> I often use similar patterns where I act on the presence of an attribute:
>>>
>>> set ? attr && set.attr <=> attrByPath ["attr"] false set
>
> Yes, that's another common use case.
>
>>> The next question is how to handle multiple level like `attrByPath
>>> ["a" "b" "c"] default as', one possible way is to attribute selections
>>> inside the name of the selected attribute.
>>>
>>> as.{a.b.c ? default}
>
> I don't find this more intuitive than "as.a.b.c or default".
>
> Also, given that the question mark already has two different meanings
> (unfortunately), it shouldn't be used for a third.
Meaning of "?":
- (set ? attr): Check if the set posses an attribute.
- (s...@{attr ? default}: ...): Check if the set posses an attribute,
otherwise set it to a default value.
- (set.{attr ? default}) Check if the set posses an attribute and
return its value, otherwise return the default value.
what I see is that the "?" is associated to a check of the presence of
the attribute, and when it is placed inside brackets and after the
attribute this means that you define a default value.
> Same goes for {...}, which is also already taken. {x ? default} looks too
> much
> like a function definition.
Indeed, and that's the reason for it. Keep things familiar and not confusing.
>> in addition to this sugar, you can add dynamic name computation sugar:
>>
>> set.<name>
>
> This is an orthogonal issue (not opposed to it btw), but it would be more
> straightforward to just allow
>
> set."${expr}"
but ` "${expr}" ' can be rewritten into ` expr ', which could be confusing.
--
Nicolas Pierron
http://www.linkedin.com/in/nicolasbpierron
Donald Knuth - I can't go to a restaurant because I keep looking at
the fonts on the menu.
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