For years I've laboured under the delusion that nouns (i.0) and (0$0) are
identical in all respects, and will pass any tests designed to discriminate
between them.
However 5!:5 can tell the difference:
5!:5 <'z' [z=: i.0
i.0
5!:5 <'z' [z=: 0$0
0$0
Nor, it seems, is there any fooling it:
5!:5 <'z' [z=: 5}.5{.i.0
i.0
5!:5 <'z' [z=: 6}.5{.i.0
i.0
5!:5 <'z' [z=: 5}.5{.0$0
0$0
5!:5 <'z' [z=: 6}.5{.0$0
0$0
How does 5!:5 know? Is this Just One of Those Things? Or is there some
deliberate logic behind this subtle difference between (0$0) and (i.0)?
Does this difference emerge in other ways – ones which might impact
practical tasks?
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