Patrick R. Michaud wrote:
On Wed, Oct 27, 2010 at 08:55:36PM -0700, Darren Duncan wrote:
Stephen Mosher (via RT) wrote:
Attached is a diff against rakudo/src/core/Any-list.pm which adds support to
reduce() for higher-arity functions. It ensures arity-list agreement and is
generally safe. Other than the test, the functionality was already
present... it needed two lines commented out, two uncommented. Since tests
passed and there were no explanatory comments in the file, jnthn suggested I
mail in a diff. Here it is.
What is a common or fundamentally important example of an N-adic
function whose base operation takes 3 or more operands, such that
reduce() would be useful?
At one point we had the higher-arity capability in reduce(), and then
took it out because it didn't seem to make much sense. So, I agree with
Darren that we need to see a use case or example (or otherwise some
"approval" in the spec) before we restore this capability.
I can say that if the desire is to have reduce() wrap a function with 2 main
parameters (which the elements of the input list go to) plus 1..N extra
configuration parameters, then that can be handily dealt with by using a curried
version of the base function that supplies the config params, so that then there
are just 2 params left for reduce() to work with as usual.
While I throw that out there, I'm assuming that the higher-arity subject here is
about taking 3 or more elements of the input list at once to feed the function,
and its not about config params.
Do any meta-operator syntaxes let you define the base function inline such as if
it would be a closure, or do they rightly only work for pre-defined symbols and
you'd have to use a foo() format version of reduce for anything more complicated?
-- Darren Duncan
