Re: Dynamic formulae calculation in RPG -- RPG400-L

Our company has a similar situation: Local taxes in some states on someproduct classifications. And the localities each have their own methodfor the same product.

Sharing the code would be too cumbersome and, probably, not help you alot. What I can share is an outline of the method.

First, a customer may be taxed by more than one locality (city, county,school board, your favorite here). There is an adjunct to the CustomerMaster which defines the localities under which the customer falls.

The hard part is classifying the product mix that works across the board.Next we defined the methods used to tax each product class. Forexample, some tax the wholesale price (our price), some tax the retailprice (like we have any control on this!), some tax by weight, etc.

Then a Locality Tax Rules table was defined. Basic layout: State, Localcode, product class, tax method, tax factor.For example: AL + 79005 + Cigars + Per cigar + $.05, which says somecity in Alabama charges 5 cents per cigar.

The invoicing program, as well as customer inquiries, use a serviceprogram to retrieve the tax rate and add it to the price. As Glennsaid, it should be simple. However, by isolating the tax methods to aservice program and each method to a subprocedure, that is exactly whatis done. Once the service program has been tested and validated, theprogrammer working on the invoice program has no reason to look at theservice program.

We have had to add new methods (geez, you can't catch everything), butthose went into the service program as a new subprocedure. Only thatsubprocedure is subjected to testing. The most complicated subprocedureis no more than 10 lines of calcs.

This process also uses one of my favorite programming methods:Table-Driven logical. Adding a new customer in an existing taxjurisdiction requires only linking the customer to the local code;adding a new locality requires only adding it to the Locality tax Rulestable.

I wrestled with this problem for about a month because I, too, wanted itto be simple. While this is not the only way to do it, it was only whenI quit looking at the details and looked at the big picture that I cameto the realization that each local tax rule was a method (subprocedure).


        * Jerry C. Adams
*IBM System i5/iSeries Programmer/Analyst
B&W Wholesale Distributors, Inc.* *
voice
        615.995.7024
fax
        615.995.1201
email
        jerry@xxxxxxxxxxxxxxx <mailto:jerry@xxxxxxxxxxxxxxx>



Glenn Gundermann wrote:

Ewart,

You should keep it simple and easy to read, hence easy to modify and easy
to debug by coding it exactly how you have it written down in your
requirements:
/free
 Base = Qty * Price;
 Tax1 = Base * .02;
 Tax2 = Tax1 * .03;
 Total = Base + Tax1 + Tax2;
/end-free

You could of course make it impossible for the next programmer to
understand what you are doing:
/free
 Total = Qty * Price * 1.0206;
/end-free

Glenn Gundermann
ggundermann@xxxxxx
(647) 272-3295

Hello All,

We have a complicated Invoice calculation process where a lot local taxes
are to be considered. In order to make these calculations dynamic I plan
to do the calculations using dynamic formulas so that any future changes
can be considered.

Eg:

Description             Name            Formula         Value
Base value              Base            Qty * price             1000
Tax1 20% of base        Tax1            Base * .02              20
Tax2 30% of Tax1        Tax2            Tax1 * .03              0.6
Total                   Total           Base + Tax1 + Tax2      1020.6


Has anyone built something like that & can share the code - I can save
some time.

Thanks & best regards
Ewart