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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Do not modify this file since it was automatically generated from:
%
% sourceTo.R
%
% by the Rdoc compiler part of the R.oo package.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\name{sourceTo}
\alias{sourceTo.default}
\alias{sourceTo}
\title{Parses and evaluates code from a file or a connection}
\usage{
\method{sourceTo}{default}(file, path=NULL, chdir=FALSE, ..., local=TRUE, envir=parent.frame(),
modifiedOnly=FALSE)
}
\description{
Parses and evaluates code from a file or a connection.
This has the same effect as if \code{source(..., local=TRUE)} would have
been called from within the given environment.
This is useful when setting up a new local working environment.
}
\arguments{
\item{file}{A \code{\link[base:connections]{connection}} or a \code{\link[base]{character}} string giving the pathname
of the file or URL to read from.}
\item{path}{An optional \code{\link[base]{character}} string giving the path to the file.
Ignored if \code{file} is a connection.}
\item{chdir}{If \code{\link[base:logical]{TRUE}} and \code{file} is a pathname, the \R
working directory is temporarily changed to the directory
containing \code{file} for evaluating.}
\item{...}{Arguments to \code{\link[base]{source}}(). If argument \code{file} is
not explicitly given, the first argument is assumed to be the
\code{file} argument. This argument is converted into a string by
\code{as.character()}.
}
\item{local}{If \code{\link[base:logical]{FALSE}}, evaluation is done in the global environment,
otherwise in the calling environment.}
\item{envir}{An \code{\link[base]{environment}} in which \code{\link[base]{source}}() should be
called. If \code{\link[base]{NULL}}, the global environment is used.}
\item{modifiedOnly}{If \code{\link[base:logical]{TRUE}}, the file is sourced only if modified
since the last time it was sourced, otherwise regardless.}
}
\value{
Return the result of \code{\link[base]{source}}().
}
\section{Hooks}{
This methods recognizes the hook \code{sourceTo/onPreprocess}, which
is called after the lines in file has been read, but before they have
been parsed by the \R parser, cf. \code{\link[base]{parse}}().
An \code{onPreprocess} hook function should take a \code{\link[base]{character}} \code{\link[base]{vector}}
of code lines and return a \code{\link[base]{character}} \code{\link[base]{vector}} of code lines.
This can for instance be used to pre-process R source code with special
directives such as \code{\link{VComments}}.
Note that only one hook function can be used for this function, otherwise
an error is generated.
}
\examples{
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Example 1
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
cat("=== Example 1 ================================================\n")
foo <- function(file, ...) {
cat("Local objects before calling sourceTo():\n")
print(ls())
res <- sourceTo(file, ...)
cat("Local objects after calling sourceTo():\n")
print(ls())
}
cat("Global objects before calling foo():\n")
lsBefore <- NA
lsBefore <- ls()
foo(file=textConnection(c('a <- 1', 'b <- 2')))
cat("Global objects after calling foo():\n")
stopifnot(length(setdiff(ls(), lsBefore)) == 0)
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Example 2 - with VComments preprocessor
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
cat("=== Example 2 ================================================\n")
preprocessor <- function(lines, ...) {
cat("-----------------------------------------\n")
cat("Source code before preprocessing:\n")
displayCode(code=lines, pager="console")
cat("-----------------------------------------\n")
cat("Source code after preprocessing:\n")
lines <- VComments$compile(lines)
displayCode(code=lines, pager="console")
cat("-----------------------------------------\n")
lines
}
oldHooks <- getHook("sourceTo/onPreprocess")
setHook("sourceTo/onPreprocess", preprocessor, action="replace")
code <- c(
'x <- 2',
'#V1# threshold=-1',
'#Vc# A v-comment log message',
'print("Hello world")'
)
fh <- textConnection(code)
sourceTo(fh)
setHook("sourceTo/onPreprocess", oldHooks, action="replace")
}
\author{Henrik Bengtsson}
\seealso{
\code{\link{sourceDirectory}}().
\code{\link[base]{sys.source}}() and \code{\link[base]{source}}().
}
\keyword{programming}
\keyword{IO}
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