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Elite on the BBC Micro

Market: tnpr1 [Elite-A, Flight]

Name: tnpr1 [Show more] Type: Subroutine Category: Market Summary: Work out if we have space for one tonne of cargo
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * Main flight loop (Part 8 of 16) calls tnpr1

Given a market item, work out whether there is room in the cargo hold for one tonne of this item. For standard tonne canisters, the limit is given by size of the cargo hold of our current ship. For items measured in kg (gold, platinum), g (gem-stones) and alien items, there is no limit. Arguments: X The type of market item (see QQ23 for a list of market item numbers) Returns: A The new number of items of type X in the hold C flag Returns the result: * Set if there is no room for this item * Clear if there is room for this item
\ --- Mod: Whole section added for Elite-A: -----------> .tnpr1 CPX #16 \ If we are checking whether to add alien items (item BEQ n_aliens \ type 16), jump to n_aliens to skip the following two \ instructions CPX #13 \ If X >= 13, then X = 13, 14 or 15 (gold, platinum or BCS l_2b04 \ gem-stones), for which there is no storage limit, so \ jump to l_2b04 to signal that there is room for this \ item .n_aliens LDY #12 \ Here we count the tonne canisters we have in the hold \ and add 1 to see if we have enough room for one more \ tonne of cargo, using Y as the loop counter, starting \ with Y = 12 SEC \ Set the C flag, so the addition below has one extra, \ representing the extra tonne we want to try to add LDA QQ20+16 \ Set A to the number of alien items we already have in \ the hold .l_2af9 ADC QQ20,Y \ Set A = A + the number of tonnes we have in the hold \ of market item number Y BCS n_cargo \ If the addition overflowed, jump to n_cargo to return \ from the subroutine with the C flag set, as the hold \ is already full DEY \ Decrement the loop counter BPL l_2af9 \ Loop back to add in the next market item in the hold, \ until we have added up all market items from 12 \ (minerals) down to 0 (food) CMP new_hold \ If A < new_hold then the C flag will be clear (we have \ room in the hold) \ \ If A >= new_hold then the C flag will be set (we do \ not have room in the hold) .n_cargo RTS \ Return from the subroutine .l_2b04 \ If we get here then the item is gold, platinum or \ gem-stones, for which there is no storage limit, and \ the C flag is set LDA QQ20,X \ Set A to the number of units of this item that we \ already have in the hold ADC #0 \ The C flag is set, so this adds one for the item we \ just scooped RTS \ Return from the subroutine \ --- End of added section ---------------------------->