Calculating the cost of inventory kits

Below is the logic which can be used to calculate the cost of an inventory item (kit) which is made up of other inventory items. The cost of these kits will change when the parts used to make them change. To get the cost, we use a function that calls itself.

Look at the code sample below. We first call this function with the inventory part number that is a kit. The function will then loop through the kit table to find all the inventory items which are used in this kit. For each item in the kit, it calls itself. We do this because a kit can be used as a part for a different kit.

Code Sample

 Function GetPartCost Integer iPartNum Returns Number
   Number nCost nTotal
   Clear Inv
   Move iPartNum to Inv.Number
   Find eq Inv by Index.1
   If (Found) Begin
       If (Inv.Kit="Y") Begin
           Clear Kit
           Move Inv.Number to Kit.PartNum
           Find ge Kit by Index.1
           If (Found) Indicate Found as (Kit.PartNum=Inv.Number)
           While (Found)
               // Function calls itself with new part number
               // beware of kits containing themself.
               Get GetPartCost Kit.KitPartNum to nCost
               Add (Kit.Qty*nCost) to nTotal
               Find gt Kit by Index.1
               If (Found) Indicate Found as (Kit.PartNum=Inv.Number)
           Loop
           // Return the kit's total cost
           Function_Return nTotal
       End
       Else Begin
           // Return the item's cost
           Function_Return Inv.Cost
       End
   End
   Else Begin
       Error 999 ("Part not found: "+String(iPartNum)) 
       Function_Return 0
   End
 End_Function

Example

You are a restaurant owner and you want to know what each of your meals cost. One of the items on your menu is a hamburger. The logic might look something like this:

Famous Dave's Sliders
    1 Homemade Kaiser Roll
    1/3 pound Ground Sirloin
    1 slice of American Cheese
    1 slice of Sharp Cheddar Cheese
      Lettuce
    2 slices of Tomato
    3 ounces of Secret Sauce
    8 ounces of Steak Fries
    1 Pickle Wedge  

The Kaiser Roll and the Special Sauce are kits, because you make them. So you also need to determine their cost.

Kaiser Rolls
    1 pound Flour
    2 cups Water
    1/3 cup Sugar
    12 ounces of yeast
    1/4 cup Extra Virgin Olive Oil

Special Sauce
   1 Tbsp Ingredient A
   1 cup Ingredient B
   1/2 Tbsp Ingredient C
   1/2 Tbsp Ingredient D
   3 ounces Ingredient E
   1 Tbsp Ingredient F
   1 tsp Ingredient G

So, by calling the GetPartCost of the main menu item, it will automatically traverse all kits to get to the root items and return their cost.

GetPartCost Famous Dave's Sliders
  GetPartCost Homemade Kaiser Roll
    GetPartCost Flour
    GetPartCost Water
    GetPartCost Sugar
    GetPartCost Yeast
    GetPartCost Olive Oil
  GetPartCost Ground Sirloin
  GetPartCost American Cheese
  GetPartCost Sharp Cheddar Cheese
  GetPartCost Lettuce
  GetPartCost Tomato
  GetPartCost Secret Sauce
    GetPartCost Ingredient A
    GetPartCost Ingredient B
    GetPartCost Ingredient C
    GetPartCost Ingredient D
    GetPartCost Ingredient E
    GetPartCost Ingredient F
    GetPartCost Ingredient G
  GetPartCost Steak Fries
  GetPartCost Pickle Wedge