AIPS NRAO AIPS HELP file for FOR in 31DEC18



As of Mon Jun 18 14:43:15 2018



HELP SECTION

FOR
Type:  Verb
Use:   To establish an iterative loop, similiar to DO loops in FORTRAN
       or PL/I.  This construction may be used in procedures or in
       immediate execution mode.  In immediate mode, all statements
       must be on the same line.
Grammar:  FOR variable = start TO fini BY increment
             statement1; statement2;... ; END
       where 'variable' is a scalar variable that will change each
       time through the loop, beginning at 'start', have 'increment'
       added to it each time through the loop (the increment may be
       positive or negative) and will end when the next loop would be
       executed with 'variable' greater than (increment > 0; less than
       with increment < 0) 'fini'.  Note that the loop will be
       executed at least once no matter what the start, fini and
       increment parameters are. If the BY section is omitted, the
       increment will default to 1.

       Statementi are AIPS statements.  These statements may not
       have an omittted optional immediate numeric argument.  Such
       statements depend on the POPS stack being empty in the absence
       of the argument.  But the FOR loop uses the stack for the
       'fini' and 'increment' values and so the stack is not empty.
       Thus TVON with no argument will see a non-empty stack and
       assume that it is getting an immediate argument from the stack.
       Use in this case TVON(2**(TVCHAN-1)) inside your loop.

       Verbs of this sort include EHEX, GROFF, GRON, HUEWEDGE,
       IMWEDGE, REHEX, TVOFF, TVON, TVWEDGE.

Examples:  FOR I = 1 TO 10; SUM = SUM + A(I); END
           FOR I = K+3 TO K BY -1; A(I+1) = A(I); END
       In the first example SUM will be incremented by the sum
       of the first 10 elements in array A.  The second example
       will shift the section of array A between A(K) and A(K+3)
       forward 1 element.

EXPLAIN SECTION


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