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Expand a bit on Boolean + missing, closes #1454

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mine-cetinkaya-rundel 2023-05-09 22:57:02 -04:00
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logicals.qmd
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@ -243,9 +243,11 @@ df |>
)
```
To understand what's going on, think about `NA | TRUE`.
To understand what's going on, think about `NA | TRUE` (`NA` or `TRUE`).
A missing value in a logical vector means that the value could either be `TRUE` or `FALSE`.
`TRUE | TRUE` and `FALSE | TRUE` are both `TRUE`, so `NA | TRUE` must also be `TRUE`.
`TRUE | TRUE` and `FALSE | TRUE` are both `TRUE` because at least one of them is `TRUE`.
`NA | TRUE` must also be `TRUE` because `NA` can either be `TRUE` or `FALSE`.
However, `NA | FALSE` is `NA` because we don't know if `NA` is `TRUE` or `FALSE`.
Similar reasoning applies with `NA & FALSE`.
### Order of operations