On Feb 4, 7:21 am, MikeM <michael.messini...@invista.com> wrote:
> > Other than that, there is just the general loss of nil-punning. This
> > was the theoretical problem that kept me from making this tradeoff
> > earlier. I'm very much interesting in hearing from those for whom the
> > lazy branch represents a real problem due to loss of nil punning.
>
> To preserve nil-punning, could the 'if' special form be changed to
> internally perform the equivalent of the seq call when presented with
> a sequence? Since more is guaranteed to never return nil, in the
> context of an 'if', a seq call would always be appropriate. I suppose
> there's a performance hit for checking whether the argument is a
> Sequence before calling seq on it, but instanceof is supposed to be
> very fast with hotspot.
I don't think a fundamental primitive like 'if' could be burdened with
such a check. Also, most collections can be supplied when their seq is
required, but what would this return?
(if [] true false)
I'd hate to lose the ability to distinguish between an empty
collection and nothing.
Rich
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