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Home -> Community -> Usenet -> comp.databases.theory -> Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Thu, 23 Jun 2005 06:15:24 GMT
Message-ID: <0ssue.127522$jg2.7110724@phobos.telenet-ops.be>


VC wrote:
> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:UGiue.127257$mY2.7061611_at_phobos.telenet-ops.be...
>

>>vc wrote:

>
> [...]
>
>>>But let's not sidetrack to XQuery,  rather tell me what 'print' is in
>>>Daplex without drawing analogies with XQuery.  Just give a definition
>>>if you please.
>>
>>The identity function. The print is only there to indicate that you 
>>produce a value, so you can simply translate it to the expression that 
>>produces that value if you makes sure that they are concatenated for each 
>>value that you iterate over.

>
> I do not understand this. I tried different interpretation but none fits.
> The closest translation might be:
>
> "' for each' denotes a list comprehension; 'print' is a monadic unit
> (identity ?) presumably applied to the constructed list. Is that so ? Or
> you meant something different by 'identity' ?

The expression "for each x in e1 print e2" denotes "[ e2 | x <- e1 ]". Why do you think that apart from this there is some need to give a separate definition of "what print is in DAPLEX"?

Received on Thu Jun 23 2005 - 01:15:24 CDT

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