cumsub

cumsub(..), process

def process cumsub(
    item:     text,
    stock:    number,
    quantity: number,
    rank:     number)  : number

The cumsub() process computes the remaining stock for each item by processing grid lines grouped into bundles ordered by increasing rank. For each bundle, if the available stock is sufficient to cover the required quantity for all grid lines, it decrements the stock; otherwise, it marks the bundle as unpurchased.

It takes 4 vectors corresponding to the following parameters:

• item: the item identifier. All grid lines sharing the same value belong to the same item.
• stock: the initial stock for the item. All grid lines for the same item should have identical stock values.
• quantity: the required quantity for purchasing the grid line.
• rank: the bundle identifier. Grid lines with the same rank form a bundle, and each (item, rank) pair must be unique. Bundles are processed in order of increasing rank.

Initially, the stock is set from the stock vector. For each bundle, the process checks if the current stock is sufficient to cover the quantity required by all grid lines. If so, it decrements the stock for each item and assigns the updated value to the corresponding grid lines. Otherwise, if there is insufficient stock, the function leaves the stock unchanged and outputs -(S+1) for each grid line, where S is the current remaining stock. This negative result signals that the grid line was not purchased and indicates the missing quantity via the expression quantity + S + 1.

Example

table G = with
  [| as Item, as Stock, as Quantity, as Rank |]
  [| "A", 10, 4, 1 |]
  [| "B", 5, 2, 1 |]
  [| "A", 10, 3, 2 |]
  [| "B", 5, 3, 2 |]
  [| "A", 10, 2, 3 |]
  [| "B", 5, 1, 4 |]

G.Remaining = cumsub(G.Item, G.Stock, G.Quantity, G.Rank)

show table "Result Inventory" with
  G.Item
  G.Stock
  G.Quantity
  G.Rank
  G.Remaining

Which produces the following output: