OpenEuphoria

2. Re: Math with sequences and single values

• Posted by jaygade Mar 13, 2011
• 2486 views

 
-- Now, a REAL invoice program would probably use EDS or an external database 
-- system and not even worry about sequences in this way exactly. 
 
include std/math.e 
 
-- Return a price or a list of prices changed by the amount in change. 
-- Note: a discount must be negative, a markup postive. If the discount or 
-- markup are on a per-item basis then price and change must be the same length. 
-- Change is expressed as a decimal indicating a percentage markup or markdown. 
function priceChange(object price, object change = 0) 
	integer lpr, lch 
	object total 
 
	if sequence(price) and sequence(change) then 
		lpr = length(price) 
		lch = length(change) 
 
		-- ensure sequences are the same size by padding with 0s. 
		if lpr < lch then 
			price &= repeat(0, lch - lpr) 
		else 
			change &= repeat(0, lpr - lch) 
		end if 
 
	end if 
 
	total = price * (1 + change) 
	 
	return total 
end function 
 
-- This is the equivalent of Vinoba's original "invoice()" function 
function item_total(object sprice, object squantity) 
	integer lsp, lsq 
	object sitemcost 
 
	if sequence(sprice) and sequence(squantity) then 
		lsp = length(sprice) 
		lsq = length(squantity) 
 
		-- ensure sequences are the same size by padding with 0s. 
		if lsp < lsq then 
			sprice &= repeat(0, lsq - lsp) 
		else 
			squantity &= repeat(0, lsp - lsq) 
		end if 
	end if 
 
		sitemcost = sprice * squantity 
 
		return sitemcost 
 
end function 
 
-- Print out the subtotals for each item purchased. Could be re-written to 
-- return strings or sequences or html or whatever instead. 
procedure invoice(sequence sitems, object subtotals) 
	integer lsi, lsu 
 
	if atom (subtotals) then 
		subtotals = {subtotals} -- promote subtotals to a sequence 
	end if 
 
	lsi = length(sitems) 
	lsu = length(subtotals) 
 
	if lsi < lsu then 
		sitems &= repeat("", lsu - lsi) 
	else 
		subtotals &= repeat(0, lsi - lsu) 
	end if 
 
	-- Really, we should have "item, quantity, price, total" but we're not 
	-- doing that complicated. If so then I would refactor this whole thing. 
	for i = 1 to lsi do 
		printf(1, "Item: %s Total: %.2f \n", {sitems[i], subtotals[i]}) 
	end for 
	puts(1, "\n") 
		 
end procedure 
 
 
-- Main 
sequence spurchages = { "Screws", "Nails", "Rivets" } 
sequence spr = {7.34, 2.54, 6.72} 
object squan = 12 -- buy 12 of everything. 
 
sequence sdetails 
sdetails = item_total(spr, squan) 
? sdetails -- the sum cost of each item 
? sum(sdetails) -- the total purchase 
invoice(spurchages, sdetails) 
 
squan = { 12, 10, 20 } -- buy different quantities of each thing. 
sdetails = item_total(spr, squan) 
? sdetails 
? sum(sdetails) 
invoice(spurchages, sdetails) 
 
sequence disprices = priceChange(spr, -0.15) -- discount everything 15% 
sdetails = item_total(disprices, squan) 
? sdetails 
? sum(sdetails) invoice(spurchages, sdetails) 
 
disprices = priceChange(spr, {-0.10, 0, -0.20}) -- discount by different amounts 
sdetails = item_total(disprices, squan) 
? sdetails 
? sum(sdetails) 
invoice(spurchages, sdetails) 
 

Not perfect, but it demonstrates what we've been talking about.

BTW, the example program you posted would fail, or at least the invoice() method would if the sequences sprice and squantity were different lengths anyway.

This program - while a simplification, but that's what we're working with here - shows operations on sequences and single values and operations on sequences and sequences. One caveat with regards to operations on two sequences is that they must have the same length and shape. The interpreter doesn't assume that you haven't made a mistake and silently pad your shorter sequences with zeroes or empty strings if they don't match. That's up to the programmer to do.

4. Re: Math with sequences and single values

• Posted by ChrisB (moderator) Mar 14, 2011
• 2505 views

Hi

Coming in late, but I agree - Vinoba's making his requirements far more complicated than they need to be.

IMHO, each item should be a Record in a Table with each property a Field (price, tax/VAT, discount, etc), then the pricing of each item should act on the items Fields. Ie using a database.

Secondly, and forgive me if I'm wrong, but if each priced up item has a variable number of sequences for the final 'invoice' calculation, then that's going to lead to a lot of nightmares anyway. Again IMHO, each 'invoiced up' item should have a fixed number of items within the sequence, and it's often best to assign a constant to each sequence number, eg

constant PRICE = 1, TAX = 2, DISCOUNT = 3 (etc)

item[PRICE] = 20
item[TAX] = item[PRICE] * current_tax

etc

just my 2p worth

Chris