PAR_GTD0L obtains a scalar logical value, with a dynamic default defined, and has the capability of handling a null status. Thus the following obtains a value from the parameter SWITCH and stores it in the variable called POWER. The dynamic default is .TRUE..
NULL = .FALSE. CALL PAR_GTD0L( 'SWITCH', .TRUE., NULL, POWER, STATUS )
The third argument is the same as we met in Section . If
we reverse the polarity of NULL, PAR_GTD0L will assign the dynamic
default to POWER whenever the parameter is in the null state, and
returns with STATUS set to SAI__OK. To reiterate NULL=.TRUE. should
only be used when the dynamic default will always give
reasonable behaviour in the application. This is highly likely for a
logical value.
PAR Interface to the ADAM Parameter System