as_mapper is the powerhouse behind the varied function
specifications that most purrr functions allow. It is an S3
generic. The default method forwards its arguments to
rlang::as_function().
as_mapper(.f, ...)
# S3 method for class 'character'
as_mapper(.f, ..., .null, .default = NULL)
# S3 method for class 'numeric'
as_mapper(.f, ..., .null, .default = NULL)
# S3 method for class 'list'
as_mapper(.f, ..., .null, .default = NULL)A function, formula, or vector (not necessarily atomic).
If a function, it is used as is.
If a formula, e.g. ~ .x + 2, it is converted to a function.
No longer recommended.
If character vector, numeric vector, or list, it is
converted to an extractor function. Character vectors index by
name and numeric vectors index by position; use a list to index
by position and name at different levels. If a component is not
present, the value of .default will be returned.
Additional arguments passed on to methods.
Optional additional argument for extractor functions
(i.e. when .f is character, integer, or list). Returned when
value is absent (does not exist) or empty (has length 0).
.null is deprecated; please use .default instead.
as_mapper(\(x) x + 1)
#> function (x)
#> x + 1
#> <environment: 0x57126e7a19f0>
as_mapper(1)
#> function (x, ...)
#> pluck_raw(x, list(1), .default = NULL)
#> <environment: 0x57126e7dbad0>
as_mapper(c("a", "b", "c"))
#> function (x, ...)
#> pluck_raw(x, list("a", "b", "c"), .default = NULL)
#> <environment: 0x57126e816c38>
# Equivalent to function(x) x[["a"]][["b"]][["c"]]
as_mapper(list(1, "a", 2))
#> function (x, ...)
#> pluck_raw(x, list(1, "a", 2), .default = NULL)
#> <environment: 0x57126e85dd20>
# Equivalent to function(x) x[[1]][["a"]][[2]]
as_mapper(list(1, attr_getter("a")))
#> function (x, ...)
#> pluck_raw(x, list(1, function (x)
#> attr(x, attr, exact = TRUE)), .default = NULL)
#> <environment: 0x57126e8a0f30>
# Equivalent to function(x) attr(x[[1]], "a")
as_mapper(c("a", "b", "c"), .default = NA)
#> function (x, ...)
#> pluck_raw(x, list("a", "b", "c"), .default = NA)
#> <environment: 0x57126e8e5218>