% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/dplyr-funcs.R
\name{register_binding}
\alias{register_binding}
\alias{register_binding_agg}
\title{Register compute bindings}
\usage{
register_binding(
  fun_name,
  fun,
  registry = nse_funcs,
  update_cache = FALSE,
  notes = character(0)
)

register_binding_agg(
  fun_name,
  agg_fun,
  registry = agg_funcs,
  notes = character(0)
)
}
\arguments{
\item{fun_name}{A string containing a function name in the form \code{"function"} or
\code{"package::function"}. The package name is currently not used but
may be used in the future to allow these types of function calls.}

\item{fun}{A function or \code{NULL} to un-register a previous function.
This function must accept \code{Expression} objects as arguments and return
\code{Expression} objects instead of regular R objects.}

\item{registry}{An environment in which the functions should be
assigned.}

\item{update_cache}{Update .cache$functions at the time of registration.
the default is FALSE because the majority of usage is to register
bindings at package load, after which we create the cache once. The
reason why .cache$functions is needed in addition to nse_funcs for
non-aggregate functions could be revisited...it is currently used
as the data mask in mutate, filter, and aggregate (but not
summarise) because the data mask has to be a list.}

\item{notes}{string for the docs: note any limitations or differences in
behavior between the Arrow version and the R function.}

\item{agg_fun}{An aggregate function or \code{NULL} to un-register a previous
aggregate function. This function must accept \code{Expression} objects as
arguments and return a \code{list()} with components:
\itemize{
\item \code{fun}: string function name
\item \code{data}: list of 0 or more \code{Expression}s
\item \code{options}: list of function options, as passed to call_function
}}
}
\value{
The previously registered binding or \code{NULL} if no previously
registered function existed.
}
\description{
The \code{register_binding()} and \code{register_binding_agg()} functions
are used to populate a list of functions that operate on (and return)
Expressions. These are the basis for the \code{.data} mask inside dplyr methods.
}
\section{Writing bindings}{

\itemize{
\item \code{Expression$create()} will wrap any non-Expression inputs as Scalar
Expressions. If you want to try to coerce scalar inputs to match the type
of the Expression(s) in the arguments, call
\code{cast_scalars_to_common_type(args)} on the
args. For example, \code{Expression$create("add", args = list(int16_field, 1))}
would result in a \code{float64} type output because \code{1} is a \code{double} in R.
To prevent casting all of the data in \code{int16_field} to float and to
preserve it as int16, do
\code{Expression$create("add", args = cast_scalars_to_common_type(list(int16_field, 1)))}
\item Inside your function, you can call any other binding with \code{call_binding()}.
}
}

\keyword{internal}
