{. and {: Extended

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{. and {: Extended | initial writing: 2001-10-22 last updated: 2004-10-26

The monads`{.` and`{:` are now defined as follows:

`{.y` ↔`0{ 1{.y`
`{:y` ↔`0{_1{.y`

Therefore,`{.y` gives the first item of`y` ,`` or an item of fills if`y` has no items; likewise`{:y` gives the last item, or fills if`y` has no items. `{.!.f` and`{:!.f` specify that the fill should be the atom`f` .
Previously,`{.y` and`{:y` signalled an index error if`y` had no items.

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