Function tests whether x
is a valid rule object, i.e., whether
it is list a list and inherits from the rmake.rule
S3 class. Instances
of rule
represent an atomic building unit, i.e. a command that
has to be executed, which optionally depends on some files or other
rules -- see rule()
for more details.
is.rule(x)
An argument to be tested
TRUE
if x
is a valid rule object and FALSE
otherwise.