%N assertl %F $MIR/src/subs/assert.for
%D Assert a boolean condition
%P pjt
%: error-handling
%B
        SUBROUTINE assertl (cond,mesg)

        CHARACTER mesg*(*)
        LOGICAL   cond

   Assertb that 'cond' is .TRUE., otherwise bail out by calling
   'bug' with 'f' and the mesg as provided in the arguments.
   Although an IF-statement will often do just as well, this make
   the code a bit smaller and readable:

   Example:
       CALL assertl(file.NE.' ','No filename specified')

   Input:
       cond    -- logical to test, if FALSE bail out
       mesg    -- message passed to bug
