purrr 0.2.4

This is a maintenance release to make purrr compatible with R 3.1.

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() and split_by() have been removed. order_by()
  conflicted with dplyr::order_by() and the complete family doesn't feel that
  useful. Use tibbles instead (#217).

• contains() has been renamed to has_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 now as_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 (using rlang::as_closure()).
  For instance + is transformed to function(.x, .y) .x + .y. This
  results in proper argument matching so that map(1:10, partial(-, .x = 5)) produces list(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
  like map(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 for lapply() (#191). This makes map() etc easier to use when
  generating functions.

• A new family of "indexed" map functions, imap(), imap_lgl() etc,
  provide a short-hand for map2(x, names(x)) or map2(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 until dplyr::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 to modify_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 calls browser()
  if f throws an error (#281).

• vec_depth() computes the depth (i.e. the number of levels of indexing)
  or a vector (#243).

• reduce2() and reduce2_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() extends stats::modifyList() to replace by position
  if the list is not named.(#201). list_merge() operates similarly
  to list_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 for dplyr::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 to cross(). The _n suffix was
  removed for consistency with pmap() (originally called map_n()
  at the start of the project) and transpose() (originally called
  zip_n()). Similarly, cross_d() has been renamed to cross_df()
  for consistency with map_df().

• every() and some() now return NA 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 character f
  comes from.

• is_numeric() and is_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 by rlang::set_names().

• safely() now actually uses the quiet 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() and detect_index() have been
  renamed from .p to .f. This is because they have mapper
  semantics rather than predicate semantics.

purrr 0.2.2

• Fix for dev tibble support.
• as_function() now supports list arguments which allow recursive indexing
  using either names or positions. They now always stop when encountering
  the first NULL (#173).
• accumulate and reduce correctly pass extra arguments to the
  worker function.

purrr 0.2.1

• as_function() gains a .null argument that for character and numeric
  values allows you to specify what to return for null/absent elements (#110).
  This can be used with any map function, e.g. map_int(x, 1, .null = NA)
• as_function() is now generic.
• New is_function() that returns TRUE only for regular functions.
• Fix crash on GCC triggered by invoke_rows().

purrr 0.2.0

New functions

• There are two handy infix functions:
  • x %||% y is shorthand for if (is.null(x)) y else x (#109).
  • x %@% "a" is shorthand for attr(x, "a", exact = TRUE) (#69).
• accumulate() has been added to handle recursive folding. It is shortand
  for Reduce(f, .x, accumulate = TRUE) and follows a similar syntax to
  reduce() (#145). A right-hand version accumulate_right() was also added.
• map_df() row-binds output together. It's the equivalent of plyr::ldply()
  (#127)
• flatten() is now type-stable and always returns a list. To return a simpler
  vector, use flatten_lgl(), flatten_int(), flatten_dbl(),
  flatten_chr(), or flatten_df().
• invoke() has been overhauled to be more useful: it now works similarly
  to map_call() when .x is NULL, and hence map_call() has been
  deprecated. invoke_map() is a vectorised complement to invoke() (#125),
  and comes with typed variants invoke_map_lgl(), invoke_map_int(),
  invoke_map_dbl(), invoke_map_chr(), and invoke_map_df().
• transpose() replaces zip2(), zip3(), and zip_n() (#128).
  The name more clearly reflects the intent (transposing the first and second
  levels of list). It no longer has fields argument or the .simplify argument;
  instead use the new simplify_all() function.
• safely(), quietly(), and possibly() are experimental functions
  for working with functions with side-effects (e.g. printed output,
  messages, warnings, and errors) (#120). safely() is a version of try()
  that modifies a function (rather than an expression), and always returns a
  list with two components, result and error.
• list_along() and rep_along() generalise the idea of seq_along().
  (#122).
• is_null() is the snake-case version of is.null().
• pmap() (parallel map) replaces map_n() (#132), and has typed-variants
  suffixed pmap_lgl(), pmap_int(), pmap_dbl(), pmap_chr(), and
  pmap_df().
• set_names() is a snake-case alternative to setNames() with stricter
  equality checking, and more convenient defaults for pipes:
  x %>% set_names() is equivalent to setNames(x, x) (#119).

Row based functionals

We are still figuring out what belongs in dplyr and what belongs in purrr. Expect much experimentation and many changes with these functions.

• map() now always returns a list. Data frame support has been moved
  to map_df() and dmap(). The latter supports sliced data frames
  as a shortcut for the combination of by_slice() and dmap():
  x %>% by_slice(dmap, fun, .collate = "rows"). The conditional
  variants dmap_at() and dmap_if() also support sliced data frames
  and will recycle scalar results to the slice size.
• map_rows() has been renamed to invoke_rows(). As other
  rows-based functionals, it collates results inside lists by default,
  but with column collation this function is equivalent to
  plyr::mdply().
• The rows-based functionals gain a .to option to name the output
  column as well as a .collate argument. The latter allows to
  collate the output in lists (by default), on columns or on
  rows. This makes these functions more flexible and more predictable.

Bug fixes and minor changes

• as_function(), which converts formulas etc to functions, is now
  exported (#123).
• rerun() is correctly scoped (#95)
• update_list() can now modify an element called x (#98).
• map*() now use custom C code, rather than relying on lapply(), mapply()
  etc. The performance characteristcs are very similar, but it allows us greater
  control over the output (#118).
• map_lgl() now has second argument .f, not .p (#134).

Deprecated functions

• flatmap() -> use map() followed by the appropriate flatten().
• map_call() -> invoke().
• map_n() -> pmap(); walk_n() -> pwalk().
• map3(x, y, z) -> map_n(list(x, y, z)); walk3(x, y, z) ->pwalk(list(x, y, z))`

First release

v0.1.0

Be explicit about "base" functions