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\details{
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\details{
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These functions apply only to packages with name spaces.
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These functions apply only to packages with name spaces.
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After loading, \code{\link{loadNamespace}} looks for a hook function named
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After loading, \code{\link{loadNamespace}} looks for a hook function named
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\code{.onLoad} and runs it before sealing the namespace and processing
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\code{.onLoad} and runs it before sealing the namespace and processing
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exports. Note that the code is run without the package being on the
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search path, so objects in the package need to be referred to using the
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double colon operator.
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exports.
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If a name space is unloaded (via \code{\link{unloadNamespace}}),
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If a name space is unloaded (via \code{\link{unloadNamespace}}),
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a hook function \code{.onUnload} is run before final unloading.
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a hook function \code{.onUnload} is run before final unloading.
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Note that the code in \code{.onLoad} and \code{.onUnload} is run
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without the package being on the search path, but (unless circumvented)
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lexical scope will make objects in the namespace and its imports
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visible. (Do not use the double colon operator in \code{.onLoad} as
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exports have not been processed at the point it is run.)
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When the package is attached (via \code{\link{library}}), the hook
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When the package is attached (via \code{\link{library}}), the hook
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function \code{.onAttach} is called after the exported functions are
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function \code{.onAttach} is called after the exported functions are
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attached. This is less likely to be useful than \code{.onLoad}, which
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attached. This is less likely to be useful than \code{.onLoad}, which
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should be seen as the analogue of \code{\link{.First.lib}} (which is only
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should be seen as the analogue of \code{\link{.First.lib}} (which is only
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used for packages without a name space).
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used for packages without a name space).
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\code{.onLoad}, \code{.onUnload} and \code{.onAttach} are looked for
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\code{.onLoad}, \code{.onUnload} and \code{.onAttach} are looked for
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as internal variables in the name space and should not be exported.
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as internal variables in the name space and should not be exported.
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A function \code{\link{.Last.lib}} will be called when the package is
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If a function \code{\link{.Last.lib}} is visible in the package, it
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detached: this does need to be exported.
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will be called when the package is detached: this does need to be exported.
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Anything needed for the functioning of the name space should be
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Anything needed for the functioning of the name space should be
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handled at load/unload times by the \code{.onLoad} and
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handled at load/unload times by the \code{.onLoad} and
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\code{.onUnload} hooks. For example, shared libraries can be loaded
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\code{.onUnload} hooks. For example, shared libraries can be loaded
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(unless done by a \code{useDynib} directive in the \code{NAMESPACE}
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(unless done by a \code{useDynib} directive in the \code{NAMESPACE}
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