dep_prev: Make later chunks depend on previous chunks
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.Value
NULL
; the internal dependency structure is updated
as a side effect.
References
http://yihui.name/knitr/demo/cache/