Re: Reflection on the special telco of CSVW

On 14 Sep 2014, at 11:44 , Andy Seaborne <andy@apache.org> wrote:

> On 14/09/14 08:39, Ivan Herman wrote:
>> The complexity of alt-1 comes from, e.g., flow control. But not only.
>> If we allow for a, say, replace, we would have to have a syntax (and
>> processing) of extra parameters. One extra step may be something
>> like
>> 
>> {{name.filter1("regexp").filter2}}
>> 
>> which may still work (and, of course, it may be used for other
>> purposes, too, like date formats), but would we go again one step
>> further and say something like
>> 
>> {{name.filter1({{name2}}).filter2}}
>> 
>> ie, having some sort of a recursive macro? We are heading, in my
>> view, back to Alternative 1, ie, a complex language to specify,
>> implement, test, etc. That is what I called 'floodgates'...
> 
> That's not recursion :-) just plain function nesting.

True, I stand corrected:-)

I still find it too complex for what we want to achieve...

Ivan

> 
> We may not even want that but it is not a technical problem.
> 
> Spreadsheets get their complexity because cells themselves can contain formulae and so when one cell can name another cell, it means there can be dependency loops.
> 
> In a CSV file, the cells are only atomic values and everything bottoms out without dependency loops.
> 
> 	Andy
> 
> if you want an outline proof  :-)
> 
> An evaluation algorithm, not necessarily the best, is:
> 
> 1/ Find inner most {{}}
>   if none, we're done.
> 
> 2/ Evaluate that expression.
> This is not another {{}} because that would be a "more inner".
> 
> 3/ Replace {{}} by the result.
> 
> 4/ Goto 1
> 
> That is not going to go on forever as you step out one level of {{}} each time.  No pointers, no way to write anything other than a tree.
> And you're not going to encounter an another formula while doing the evaluate because the inner most {{}} does not contains another {{}}.
> 
> if name2 is "foo"
> and name is "foobar"
> 
> {{name.stringafter({{name2}}).uppercase}}
> -->
> {{name.stringafter("foo").uppercase}}
> -->
> {{"foobar".stringafter("foo").uppercase}}
> -->
> {{"bar".uppercase}}
> -->
> "BAR"
> 
> c.f. "let" vs "letrec"
> =>
> ftp://ftp.cs.utexas.edu/pub/garbage/cs345/schintro-v14/schintro_66.html
> 
> 


----
Ivan Herman, W3C 
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