Re: [Freemarker-devel] New built-ins (`?whatever` things)... any opinions/ideas?

Wednesday, August 8, 2012, 9:52:13 AM, Denis Bredelet wrote:

> "chose" should really be "either" I think. 

  (a < b)?either(a, b)
  (a < b)?chose(a, b)

I don't know... any votes? Or an even better name?

> Not sure what's the use of ?char

Character-code arithmetic is frequently needed for converting 1, 2, 3,
etc. to 'A', 'B', 'C', etc. However, now that you ask, I can't image
any other use-cases, so I should address that directly.

  n?number_as_letter
  n?number_as_lower_letter

which would return 'A'/'a' for 1, 'Z'/'z' for 26, 'AA'/'aa' for 27,
'AB'/'ab' for 28, etc.

Speaking of which, maybe ?roman should be added too, which converts 1
to "I", 2 to "II", etc.

> or ?bin_8.

Actually I only know that converting to hexadecimal is frequently
requested. Now that I think about it, the binary-related requests was
about testing if a bit is set. So then maybe we only need:

  n?[j_]hex_[8|16|32|64]

and

  n?bit(index)

which returns a boolean.

> I like followed_by and dump
>
> Should min and max work on lists instead of single values?

They should have vararg parameter list. Also, they could work on
sequences too. Although the I guess most use-cases are with two
numbers.

-- 
Best regards,
 Daniel Dekany


> -- Denis.
>
> On 8 Aug 2012, at 08:18, Daniel Dekany <[email protected]> wrote:
>
>> I'm planning to add some new buildins to FreeMarker 2.3.x. I'm not
>> sure which of these will go to the next release, but certainly not all
>> of them (lack of time...). I would like to hear some opinions, or
>> ideas regarding better names and semantics. Also regarding what other
>> built-ins you miss.
>> 
>> boolExp?chose(whenTrue, whenFalse)
>> 
>>  This one is instead of Java's ternary operator (exp ? exp : exp), that
>>  FTL can't have due to syntactical reasons. Of course, the operators
>>  are evaluated on demand. It's like #if/#else, but it's an expression.
>> 
>> n?until(m[, step=1])
>> n?to(m[, step=1])
>>  These would deprecate the ".." operator, which was sadly
>>  mis-designed back then. They create a numerical range, always with
>>  step 1 (not -1) unless `step` was provided. "until" has exclusive end,
>>  "to" has inclusive end.
>> 
>> s?safe_substring(from[, to])
>> 
>>  Same as ?substring, but ignores out-of-ranges
>> 
>> n?char
>> 
>>  Converts UCS codepoint to character. Like 65?char is 'A'.
>> 
>> n?abs
>>  Absolute value
>> 
>> n?[bin|[j]hex|oct]_[8|16|32|64]
>>  That is ?bin_8, ?bin_16, ..., hex_8, hex_16. The difference between
>>  "hex" and "jhex" is tat the last prints with a 0x prefix.
>> 
>> n?is_nan, n?is_infinity
>>  Works only for numbers, tells if the wrapped number is float or
>>  double NaN or Infinitiy (positive or negative).
>> 
>> exp1?followed_by(exp2)
>> 
>>  This returns exp1 + exp2, but only if both are defined and are
>>  non-0-length strings. This is useful in situations like these:
>> 
>>    <title>Foo bar<#if extraTitle??> - ${extraTitle}</#if></title>
>> 
>>  or
>> 
>>    <#if statement??>${statement};</#if>
>> 
>>  That is, you want to print an optional variable and when it exists,
>>  you also want to print something before or after it. These would
>>  become to:
>> 
>>    <title>Foo bar${' - '?followed_by(extraTitle)}</title>
>> 
>>    ${statement?followed_by(';')}
>> 
>> min/max:
>> 
>>  I wonder how to add min/max functions. `n?min(m)` looks silly IMO.
>>  It could be `.min(n, m)` instead, where the initial dot is for the
>>  special-variable syntax (used for .data_model, .version and like).
>>  Only it's something most user don't know...
>> 
>> exp?dump
>> exp?dump_as_text
>> 
>>  Prints the value for debugging purposes. ?dump would print it as
>>  XHTML, while dump_as_text as text/plain.
>> 
>> -- 
>> Best regards,
>> Daniel Dekany


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