\name{dep_prev}
\alias{dep_prev}
\title{Make later chunks depend on previous chunks}
\usage{
dep_prev()
}
\value{
  \code{NULL}; the internal dependency structure is updated
  as a side effect.
}
\description{
  This function can be used to build dependencies among
  chunks so that all later chunks depend on previous
  chunks, i.e. whenever the cache of a previous chunk is
  updated, the cache of all its later chunks will be
  updated.
}
\references{
  \url{http://yihui.name/knitr/demo/cache/}
}
\seealso{
  \code{\link{dep_auto}}
}
