> > As people have said, DWIM sez [% IF array %] should be true only if array
> > contains something more than nothing.
>
> As far as I know, there's no way to do this without re-writing large parts
> of TT. Even then, I don't think it's possible.
>
> The Perl code generated for
>
> [% IF array %]
>
> looks like
>
> if ($stash->get('array'))
It is possible, although probably not a great idea. What you could do
is add a new rule to Parser.yp for a boolean expression, which is just
expr, but the action wraps the result in a function call that computes
trueness. Something like:
bool_expr: expr { "expr2boolean($_[1])" }
expr2boolean() is a sub that is a no-op for a scalar, and returns true
for non-empty array refs and hash refs.
Then you replace rules that expect boolean expressions with bool_expr,
such as IF, WHILE, the first expr in ?:, and perhaps the lhs of ||
and &&. The generated code for the IF example above would then
look like:
if (expr2boolean($stash->get('array')))
while other expressions and assignments would be unchanged.
> Perhaps the best solution is to have a '.size' method which works
> consistently across all data types:
>
> [% item.size %] # 1
> [% hash.size %] # scalar(keys %$hash)
> [% list.size %] # scalar(@$list)
>
> It's not as DWIMmy as [% IF something %], but at least you could then be
> sure that [% IF something.size %] will always work as expected.
I prefer the idea of an operator to changing the grammar. How about
".true"? That has the right connotation (check for "trueness") without
confusion over length/size etc. Then you can write:
[% IF array.true %]
Other ideas might be "nonempty" (a bit clunky) or ".boolean".
Craig
