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  matched (exactly) to the names of the elements in \code{\dots}.  If
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  matched (exactly) to the names of the elements in \code{\dots}.  If
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  there is a match then that element is evaluated unless it is missing,
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  there is a match then that element is evaluated unless it is missing,
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  in which case the next non-missing element is evaluated, so for
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  in which case the next non-missing element is evaluated, so for
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  example \code{switch("cc", a = 1, cc =, cd =, d = 2)} evaluates to
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  example \code{switch("cc", a = 1, cc =, cd =, d = 2)} evaluates to
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  \code{2}.  If there is more than one match, the first matching element
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  \code{2}.  If there is more than one match, the first matching element
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  is used.  In the case of no match, if there is a unnamed element of
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  is used.  In the case of no match, if there is an unnamed element of
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  \code{\dots} its value is returned.  (If there is more than one such
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  \code{\dots} its value is returned.  (If there is more than one such
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  argument an error is signaled.)
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  argument an error is signaled.)
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  The first argument is always taken to be \code{EXPR}: if it is named
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  The first argument is always taken to be \code{EXPR}: if it is named
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  its name must (partially) match.
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  its name must (partially) match.
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  A warning is signaled if no alternatives are provides, as this is
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  A warning is signaled if no alternatives are provided, as this is
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  usually a coding error.
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  usually a coding error.
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  This is implemented as a \link{primitive} function that only evaluates
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  This is implemented as a \link{primitive} function that only evaluates
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  its first argument and one other if one is selected.
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  its first argument and one other if one is selected.
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}
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}