Re: Parsing of numeric values

Tuesday, September 15, 2009, 4:34:22 AM, wkbutler wrote:

>
> Hello - 
> I am a bit confused on the built-in capability of FM to parse a localized
> numeric expression,

It's none. FM can convert simple "computer-audience number" strings
back to numbers, because sometimes, for purely technical reasons, you
get numbers "serialized" to text format. Parsing human-audience
numbers is out of the scope of FM, and in theory you should deal with
that in the C of MVC, not in the V. Means, although you can solve that
in the V with a TempateMethdoModelEx (or with a #function), you might
shouldn't do that.

> and before I write a custom routine for this, maybe
> there is wisdom I lack.
>
> I am trying to process a mathematical expression on the contents of a map of
> string data:
>
> ---------------
> | a |  1,111    |
> | b |  2,222    |
> ---------------
>
> so a simple expression like
>      ${a?number + b?number}  
>
> would work if the numbers were not localized, right?

At least with this concrete example, yes.

> That I have had success with.
>
> The original syntax 
>    #{a} + #{b}
>
> is deprecated according to this page in the docs
>     
> http://freemarker.sourceforge.net/docs/ref_depr_numerical_interpolation.html

It is. Don't use it.

> although trying this I get the error message:
>
>     a is not a number, it is freemarker.template.SimpleScalar

Unlike ?number, #{...} doesn't even try to convert strings to numbers.

> Using the number built-in ?c and the string built-in
> ?string.computer fail with similar messages,

These convert a number (or date, etc.) to a string, not the other way
around.

> such as "Expected hash" etc. It seems I do not understand what data
> type I am dealing with.

notANumber?string is not a hash (aNumber?string is), but the dot (.)
operator will expect a hash on its left side, hence it throws the
above error. Yeah, a but tricky...

> I would like to have have the 2 numbers added together and output with the
> default localized syntax.  Am I looking past something?

No, except maybe that, whatever view technology are you using
(FreeMarker or not) it's not something that you should do in a the
view layer of your application. At least usually it's not...

> Thanks for ideas

-- 
Best regards,
 Daniel Dekany


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