On Wed, Jun 01, 2022 at 09:27:28PM +0200, Ralf Hemmecke wrote:
> On 01.06.22 21:09, Waldek Hebisch wrote:
> >Did you ever think why 'delay' with pile works? 'delay' expects function
> >as an argument, pile as argument produces a value. Why this
> >works when produced value is _not_ a function?
>
> Oh, good that you come to it. Exactly, I would always have expected
> something like
>
> foo(...) == delay
> () + ->
> PILE
>
> There must be some magic in the compiler to silently insert that missing
> piece. Is there?
Yes. When request type is function type compiler calls
compWithMappingMode which is doing needed magic. In fact,
compWithMappingMode can handle old form of anonymous functions
with '#1', '#2', etc., but those are rejected by the parser.
However, zero argument case still works and is used with 'delay'.
I supect that the same magic that works with 'delay' breaks
'pretend' in 'lazyEval'...
--
Waldek Hebisch
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