Ian Cook created ARROW-13118:
--------------------------------
Summary: [R] Improve handling of R scalars in some nse_funcs
Key: ARROW-13118
URL: https://issues.apache.org/jira/browse/ARROW-13118
Project: Apache Arrow
Issue Type: Improvement
Components: R
Reporter: Ian Cook
Assignee: Ian Cook
Fix For: 5.0.0
Some of the functions in {{nse_funcs}} do not behave properly when passed R
scalar input in expressions in dplyr verbs. Some examples:
{code:r}
Table$create(x = 1) %>% mutate(as.character(42))
Table$create(x = 1) %>% mutate(is.character(("foo")))
Table$create(x = 1) %>% mutate(nchar("foo"))
Table$create(x = 1) %>% mutate(is.infinite(Inf))
{code}
This could be resolved by using {{build_expr()}} instead of
{{Expression$create()}}, but {{build_expr()}} is awfully heavy. The only part
of it we really need to make this work is this:
{code:r}
args <- lapply(args, function(x) {
if (!inherits(x, "Expression")) {
x <- Expression$scalar(x)
}
x
}){code}
Maybe we could make a function called {{wrap_r_scalar}}, like this:
{code:r}
wrap_r_scalar <- function(x) {
if (!inherits(x "Expression")) {
assert_that(
length(x) == 1,
msg = "Literal vectors of length != 1 not supported"
)
Expression$scalar(x)
} else {
x
}
}
{code}
and use it as needed in various of the {{nse_funcs}} functions.
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