Parse the condition string so that it can be evaluated by the cond.*
functions. Intended for internal use only.
cond.parse(names_attTbl, cond)character vector, the column (i.e. variable) names of the
attribute table returned by the function attTbl.
character string, the condition string used by the cond.*
functions to classify raster cells (see conditions).
The function returns a two-element list. The first element contains
the parsed conditions to be evaluated by the cond.* functions. The
second element defines the condition type each variable refers to.