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rlang

rlang is a collection of frameworks and APIs for programming with R.

Frameworks

Two comprehensive frameworks are implemented in rlang.

  • tidy eval, a programmable data-masking framework used in tidyverse packages like dplyr and ggplot2. As a user, you will encounter the embracing operator {{ and name injection with the glue operators "{" and "{{".

  • rlang errors, a set of tools to signal and display errors. This includes backtrace capture with global_entrace() and backtrace display with last_error() and last_warnings(). Use abort() to create errors with bullet lists, structured metadata, and error chaining support.

    The display of error messages is optimised for bullet lists and chained errors and optionally integrates with the cli package (see local_use_cli()).

Argument intake

A set of tools help you check, validate, and preprocess arguments.

  • Checking function arguments, e.g. arg_match(), check_required(), and check_exclusive().

  • Checking dots, e.g. check_dots_used() and check_dots_empty().

  • Collecting dynamic dots, e.g. list2(). These dots support splicing with !!! and name injection with the glue operators "{" and "{{".

Programming interfaces

rlang provides various interfaces for working with R and R objects.

  • The R session, e.g. check_installed(), on_load(), and on_package_load().

  • Environments, e.g. env(), env_has(), env_get(), env_bind(), env_unbind(), env_print(), and local_bindings().

  • Evaluation, e.g. inject() and eval_bare().

  • Calls and symbols, e.g. call2(), is_call(), is_call_simple(), data_sym(), and data_syms().

  • Functions, e.g. new_function() and as_function(). The latter supports the purrr-style formula notation for lambda functions.

Installation

Install the released version of rlang from CRAN:

install.packages("rlang")

Or install the development version from GitHub with:

# install.packages("pak")
pak::pkg_install("r-lib/rlang")

Code of Conduct

Please note that the rlang project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.

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Version

Install

install.packages('rlang')

Monthly Downloads

1,458,451

Version

1.0.4

License

MIT + file LICENSE

Issues

125

Pull Requests

21

Stars

531

Forks

143

Maintainer

Lionel Henry

Last Published

July 12th, 2022

Functions in rlang (1.0.4)

as_data_mask

Create a data mask
args_dots_empty

Helper for consistent documentation of empty dots
as_box

Convert object to a box
args_error_context

Documentation anchor for error arguments
arg_match

Match an argument to a character vector
are_na

Test for missing values
args_dots_used

Helper for consistent documentation of used dots
as_closure

Transform to a closure
UQ

Deprecated UQ() and UQS() operators
abort

Signal an error, warning, or message
as_environment

Coerce to an environment
call_name

Extract function name or namespace of a call
bytes-class

Human readable memory sizes
call2

Create a call
call_modify

Modify the arguments of a call
as_function

Convert to function
caller_arg

Find the caller argument for error messages
check_dots_used

Check that all dots have been used
bare-type-predicates

Bare type predicates
call_standardise

Standardise a call
call_args

Extract arguments from a call
cnd_message

Build an error message from parts
dots_n

How many arguments are currently forwarded in dots?
embrace-operator

Embrace operator {{
check_exclusive

Check that arguments are mutually exclusive
empty_env

Get the empty environment
dots_values

Evaluate dots with preliminary splicing
check_required

Check that argument is supplied
catch_cnd

Catch a condition
check_dots_empty

Check that dots are empty
box

Box a value
chr_unserialise_unicode

Translate unicode points to UTF-8
cnd_muffle

Muffle a condition
as_name

Extract names from symbols
call_inspect

Inspect a call
as_label

Create a default name for an R object
cnd_type

What type is a condition?
cnd_signal

Signal a condition object
env_binding_lock

Lock or unlock environment bindings
check_dots_empty0

Check that dots are empty (low level variant)
call_fn

Extract function from a call
as_string

Cast symbol to string
env_inherits

Does environment inherit from another environment?
call_match

Match supplied arguments to function definition
duplicate

Duplicate an R object
check_dots_unnamed

Check that all dots are unnamed
env_bind

Bind symbols to objects in an environment
env_cache

Cache a value in an environment
env_binding_are_active

What kind of environment binding?
format_error_bullets

Format bullets for error messages
env_browse

Browse environments
dyn-dots

Dynamic dots features
env_bury

Mask bindings by defining symbols deeper in a scope
cnd

Create a condition object
as_utf8_character

Coerce to a character vector and attempt encoding conversion
format_error_call

Validate and format a function call for use in error messages
env_clone

Clone or coalesce an environment
dev-notes-dots

Development notes - dots.R
defusing-advanced

Advanced defusal operators
entrace

Add backtrace from error handler
env_parent

Get parent environments
env_poke

Poke an object in an environment
env_lock

Lock an environment
enquo

Defuse function arguments
expr

Defuse an R expression
englue

Defuse function arguments with glue
fn_env

Return the closure environment of a function
expr_interp

Process unquote operators in a captured expression
exprs_auto_name

Ensure that all elements of a list of expressions are named
env

Create a new environment
env_get

Get an object in an environment
fn_fmls

Extract arguments from a function
is_condition

Is object a condition?
has_length

How long is an object?
eval_tidy

Evaluate an expression with quosures and pronoun support
flatten

Flatten or squash a list of lists into a simpler vector
env_has

Does an environment have or see bindings?
exec

Execute a function
fn_body

Get or set function body
expr_label

Turn an expression to a label
eval_bare

Evaluate an expression in an environment
env_depth

Depth of an environment chain
f_rhs

Get or set formula components
env_unlock

Unlock an environment
cnd_inherits

Does a condition or its ancestors inherit from a class?
is_call

Is object a call?
has_name

Does an object have an element with this name?
is_callable

Is an object callable?
global_prompt_install

Prompt user to install missing packages
dot-data

.data and .env pronouns
env_names

Names and numbers of symbols bound in an environment
env_unbind

Remove bindings from an environment
done

Box a final value for early termination
env_print

Pretty-print an environment
env_name

Label of an environment
expr_print

Print an expression
get_env

Get or set the environment of an object
interrupt

Simulate interrupt condition
friendly_type

Format a type for error messages
is_formula

Is object a formula?
f_text

Turn RHS of formula into a string or label
faq-options

Global options for rlang
is_environment

Is object an environment?
is_true

Is object identical to TRUE or FALSE?
invoke

Invoke a function with a list of arguments
is_symbol

Is object a symbol?
is_function

Is object a function?
local_use_cli

Use cli to format error messages
new_call

Create a new call from components
missing

Missing values
glue-operators

Name injection with "{" and "{{"
quo_expr

Squash a quosure
is_installed

Are packages installed in any of the libraries?
last_error

Last abort() error
local_error_call

Set local error call in an execution environment
last_warnings

Display last warnings
is_integerish

Is a vector integer-like?
global_entrace

Entrace unexpected errors
is_copyable

Is an object copyable?
local_options

Change global options
global_handle

Register default global handlers
new_formula

Create a formula
quo_squash

Squash a quosure
quo_label

Format quosures for printing or labelling
quosure-tools

Quosure getters, setters and predicates
missing_arg

Generate or handle a missing argument
new_quosure

Create a quosure from components
names2

Get names of a vector
is_expression

Is an object an expression?
scalar-type-predicates

Scalar type predicates
rlib_trace_spec

Backtrace specification
new_quosures

Create a list of quosures
hash

Hashing
inject

Inject objects in an R expression
set_attrs

Add attributes to an object
set_expr

Set and get an expression
op-get-attr

Infix attribute accessor and setter
on_load

Run expressions on load
return_from

Jump to or from a frame
inherits_any

Does an object inherit from a set of classes?
rlang-package

rlang: Functions for Base Types and Core R and 'Tidyverse' Features
is_dictionaryish

Is a vector uniquely named?
set_names

Set names of a vector
is_namespace

Is an object a namespace environment?
is_named

Is object named?
is_empty

Is object an empty vector or NULL?
splice-operator

Splice operator !!!
switch_type

Dispatch on base types
scoped_env

Deprecated scoped functions
scoped_interactive

Deprecated scoped_ functions
topic-condition-customisation

Customising condition messages
is_weakref

Is object a weak reference?
local_bindings

Temporarily change bindings of an environment
list2

Collect dynamic dots in a list
ns_registry_env

Return the namespace registry env
lang

Create a call
sym

Create a symbol or list of symbols
topic-embrace-constants

Why are strings and other constants enquosed in the empty environment?
topic-double-evaluation

The double evaluation problem
obj_address

Address of an R object
topic-multiple-columns

Taking multiple columns without ...
try_fetch

Try an expression with condition handlers
trace_back

Capture a backtrace
injection-operator

Injection operator !!
vec_poke_n

Poke values into a vector
is_interactive

Is R running interactively?
topic-condition-formatting

Formatting messages with cli
vector-coercion

Coerce an object to a base type
prim_name

Name of a primitive function
qq_show

Show injected expression
is_lang

Is object a call?
topic-quosure

What are quosures and when are they needed?
new_weakref

Create a weak reference
is_reference

Is an object referencing another?
is_pairlist

Is object a node or pairlist?
splice

Splice lists
rep_along

Create vectors matching the length of a given vector
stack

Get properties of the current or caller frame
raw_deparse_str

Serialize a raw vector to a string
stack-deprecated

Call stack information
string

Create a string
ns_env

Get the namespace of a package
pairlist2

Collect dynamic dots in a pairlist
parse_expr

Parse R code
names_inform_repair

Inform about name repair
new_function

Create a function
new-vector

Create vectors matching a given length
new_node

Helpers for pairlist and language nodes
op-null-default

Default value for NULL
op-na-default

Replace missing values
type-predicates

Type predicates
type_of

Base type of an object
topic-embrace-non-args

Does {{ work on regular objects?
topic-error-call

Including function calls in error messages
topic-data-mask-ambiguity

The data mask ambiguity
topic-data-mask-programming

Data mask programming patterns
zap_srcref

Zap source references
rlang_backtrace_on_error

Display backtrace on error
topic-metaprogramming

Metaprogramming patterns
with_env

Evaluate an expression within a given environment
with_handlers

Establish handlers on the stack
topic-inject

Injecting with !!, !!!, and glue syntax
rlang_error

Errors of class rlang_error
search_envs

Search path environments
vector-construction

Create vectors
topic-error-chaining

Including contextual information with error chains
wref_key

Get key/value from a weak reference object
seq2

Increasing sequence of integers in an interval
zap

Create zap objects
topic-defuse

Defusing R expressions
topic-data-mask

What is data-masking and why do I need {{?
vector-old-ctors

Retired vector construction by length
topic-inject-out-of-context

What happens if I use injection operators out of context?