Headings - part 3

Summary

Loops within Headings (i.e. a Heading which invokes itself) is supported, as it is possible to use these to set up *recursion*. However, the loops should be properly terminated, otherwise the generation process will loop forever.

The “max” and “min” operations set the running total to either the maximum or minimum of the running total and the operand.

The “and” and “or” operations are based on Booleans.

The “pass back” functions are special, as they are used to pass back values to be displayed in the columns of the invoking Heading. Note that these override the *display* of those columns, allowing these columns to be used as general purpose display, but without affecting the ongoing calculations that the calling Heading is performing.

A: It is now possible to pass back an override of the calculated operand as well ( <<op ).

A: The pass back operations can now take an empty operand, in which case they pass back the current value of the running total.

Following these operations is a list of all the operations seen so far (apart from ignore) but surrounded by square brackets. These operations are known as field-access operations. They essentially perform the same operation as the non-field access version but on a field rather than on the operand.

The final operations are the subtotal / maths ones. These operations do not use an operand (so the “On” column is disabled) and their result is shown in the Operand column.

E: Subtotal / maths functions never display a pre-op-total or post-op-total, regardless of whether the running-total is changed (which it is in the case of maths functions).

A: The “rescan if true”, “rescan if false” and "rescan if uninit" cause the heading to be re-evaluted - restarted - using the operand and style in the line instead of operand (i.e. this heading) and style in the original invocation of the heading. If the operand is omitted, then the Heading fails exactly as if the Heading had encountered a table whose value could not be found. Note that this rescanning function is very powerful in allowing you to process a heading using lots of different headings depending on whatever conditions you like. Whichever Headings you ultimately use, the Heading reported will look like the one originally invoked (in case you choose to display this).

Following the maths functions are a few date functions and finally the Boolean NOT.

Addenda / Errata