Searching

The store has an inventory table in the stack: which ingot, how many. Somebody asks for steel. The chip has to find the row – and preferably not read all entries if steel is already in fourth place.

Table with pairs#

Each entry has two values. You store them one after the other: hash at address 2i, quantity at 2i + 1. You compute the address with sll addr i 1 – shifting left once is times 2, from bit week.

Linear search#

The simplest search goes through the entries in order and compares. Hashes are whole numbers, so beq is safe here:

move found -1
move i 0
search:
sll addr i 1               # address = 2 · i
get value db addr
beq value target hit    # stop early
add i i 1
blt i COUNT search

Stopping early#

As soon as the entry is found, the chip jumps out of the loop. If steel is in fourth place, it reads four entries instead of six. With a table of 100 entries that saves half on average. If nothing is found, the loop runs to the end and found stays −1.

Minimum and maximum#

For the minimum min is enough. For the maximum you also want to know which entry it is – max cannot do that. So you compare yourself and remember value and position:

bge maxv value next       # not larger: skip
move maxv value
move maxidx i
next:

The starting values pinf and ninf make sure the first real entry always wins.