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Let's not go out of our way to return senseless results. See ruby/spec#1140
A negative `size` makes no sense at all, -infinity even less so. It is indeed the case that Ruby currently returns `-infinity` (even if you take the product of two of these senseless enumerables), but that doesn't make it a _valid spec_. Ruby does this because it is simpler to test for ±infinity than it is to test for +infinity... Other alternative implementations should _not_ attempt to mimick such behaviour. One could argue it is a bug (and `nil` should be returned maybe, but that would be the case for any negative `size`), or that the current result is acceptable because "garbage in garbage out", but nobody in their right mind would rely on this behavior and clearly returning `nil` or raising an exception are better results than returning - infinity. This PR leaves this uninteresting and ill-defined corner case as implementation dependent.
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Agree! Wondering if it makes sense to have means to specify explicitly in specs that some case has undefined behaviour or implementation-specific one? In case a CRuby behaviour is considered as not accurate? |
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A negative
sizemakes no sense at all, -infinity even less so. It is indeed the case that Ruby currently returns-infinity(even if you take the product of two of these senseless enumerables), but that doesn't make it a valid spec. Ruby does this because it is simpler to test for ±infinity than it is to test for +infinity...Other alternative implementations should not attempt to mimick such behaviour.
One could argue it is a bug (and
nilshould be returned maybe, but that would be the case for any negativesize), or that the current result is acceptable because "garbage in garbage out", but nobody in their right mind would rely on this behavior and clearly returningnilor raising an exception are better results than returning - infinity.This PR leaves this uninteresting and ill-defined corner case as implementation dependent.
Ref: marcandre/backports#192