purrr 0.2.3
Breaking changes
We noticed the following issues during reverse dependencies checks:
-
If
reduce()
fails with this message:Error: `.x` is empty, and no `.init` supplied
this is because
reduce()
now returns.init
when.x
is
empty. Fix the problem by supplying an appropriate argument to
.init
, or by providing special behaviour when.x
has length 0. -
The type predicates have been migrated to rlang. Consequently the
bare-type-predicates
documentation topic is no longer in purrr,
which might cause a warning if you cross-reference it.
Dependencies
purrr no longer depends on lazyeval or Rcpp (or dplyr, as of the
previous version). This makes the dependency graph of the tidyverse
simpler, and makes purrr more suitable as a dependency of lower-level
packages.
There have also been two changes to eliminate name conflicts between
purrr and dplyr:
-
order_by()
,sort_by()
andsplit_by()
have been removed.order_by()
conflicted withdplyr::order_by()
and the complete family doesn't feel that
useful. Use tibbles instead (#217). -
contains()
has been renamed tohas_element()
to avoid conflicts with
dplyr (#217).
pluck()
The plucking mechanism used for indexing into data structures with
map()
has been extracted into the function pluck()
. Plucking is
often more readable to extract an element buried in a deep data
structure. Compare this syntax-heavy extraction which reads
non-linearly:
accessor(x[[1]])$foo
to the equivalent pluck:
x %>% pluck(1, accessor, "foo")
Map helpers
-
as_function()
is nowas_mapper()
because it is a tranformation that
makes sense primarily for mapping functions, not in general (#298).
.null
has been renamed to.default
to better reflect its intent (#298).
.default
is returned whenever an element is absent or empty (#231, #254).as_mapper()
sanitises primitive functions by transforming them to
closures with standardised argument names (usingrlang::as_closure()
).
For instance+
is transformed tofunction(.x, .y) .x + .y
. This
results in proper argument matching so thatmap(1:10, partial(
-, .x = 5))
produceslist(5 - 1, 5 - 2, ...)
. -
Recursive indexing can now extract objects out of environments (#213) and
S4 objects (#200), as well as lists. -
attr_getter()
makes it possible to extract from attributes
likemap(list(iris, mtcars), attr_getter("row.names"))
. -
The argument list for formula-functions has been tweaked so that you can
refer to arguments by position with..1
,..2
, and so on. This makes it
possible to use the formula shorthand for functions with more than two
arguments (#289). -
possibly()
,safely()
and friends no longer capture interrupts: this
means that you can now terminate a mapper using one of these with
Escape or Ctrl + C (#314)
Map functions
-
All map functions now treat
NULL
the same way as an empty vector (#199),
and return an empty vector if any input is an empty vector. -
All
map()
functions now force their arguments in the same way that base R
does forlapply()
(#191). This makesmap()
etc easier to use when
generating functions. -
A new family of "indexed" map functions,
imap()
,imap_lgl()
etc,
provide a short-hand formap2(x, names(x))
ormap2(x, seq_along(x))
(#240). -
The data frame suffix
_df
has been (soft) deprecated in favour of
_dfr
to more clearly indicate that it's a row-bind. All variants now
also have a_dfc
for column binding (#167). (These will not be terribly
useful untildplyr::bind_rows()
/dplyr::bind_cols()
have better
semantics for vectors.)
Modify functions
A new modify()
family returns the same output of the type as the
input .x
. This is in contrast to the map()
family which always
returns a list, regardless of the input type.
The modify functions are S3 generics. However their default methods
should be sufficient for most classes since they rely on the semantics
of [<-
. modify.default()
is thus a shorthand for x[] <- map(x, f)
.
-
at_depth()
has been renamed tomodify_depth()
. -
modify_depth()
gains new.ragged
argument, and negative depths are
now computed relative to the deepest component of the list (#236).
New functions
-
auto_browse(f)
returns a new function that automatically callsbrowser()
iff
throws an error (#281). -
vec_depth()
computes the depth (i.e. the number of levels of indexing)
or a vector (#243). -
reduce2()
andreduce2_right()
make it possible to reduce with a
3 argument function where the first argument is the accumulated value, the
second argument is.x
, and the third argument is.y
(#163). -
list_modify()
extendsstats::modifyList()
to replace by position
if the list is not named.(#201).list_merge()
operates similarly
tolist_modify()
but combines instead of replacing (#322). -
The legacy function
update_list()
is basically a version of
list_modify
that evaluates formulas within the list. It is likely
to be deprecated in the future in favour of a tidyeval interface
such as a list method fordplyr::mutate()
.
Minor improvements and bug fixes
-
Thanks to @dchiu911, the unit test coverage of purrr is now much greater.
-
All predicate functions are re-exported from rlang (#124).
-
compact()
now works with standard mapper conventions (#282). -
cross_n()
has been renamed tocross()
. The_n
suffix was
removed for consistency withpmap()
(originally calledmap_n()
at the start of the project) andtranspose()
(originally called
zip_n()
). Similarly,cross_d()
has been renamed tocross_df()
for consistency withmap_df()
. -
every()
andsome()
now returnNA
if present in the input (#174). -
invoke()
uses a more robust approach to generate the argument list (#249)
It no longer uses lazyeval to figure out which enviroment a characterf
comes from. -
is_numeric()
andis_scalar_numeric()
are deprecated because they
don't test for what you might expect at first sight. -
reduce()
now throws an error if.x
is empty and.init
is not
supplied. -
Deprecated functions
flatmap()
,map3()
,map_n()
,walk3()
,
walk_n()
,zip2()
,zip3()
,zip_n()
have been removed. -
pmap()
coerces data frames to lists to avoid the expensive[.data.frame
which provides security that is unneeded here (#220). -
rdunif()
checks its inputs for validity (#211). -
set_names()
can now take a function to tranform the names programmatically
(#276), and you can supply names in...
to reduce typing even more
more (#316).set_names()
is now powered byrlang::set_names()
. -
safely()
now actually uses thequiet
argument (#296). -
transpose()
now matches by name if available (#164). You can
override the default choice with the new.names
argument. -
The function argument of
detect()
anddetect_index()
have been
renamed from.p
to.f
. This is because they have mapper
semantics rather than predicate semantics.