Support automated lot price inferrence

[xkikeg]

Currently there's no automated support for lot price computation, but that's nice to have.

Difficulties

Ambiguous ways

There are several ways to compute the lot price. By the article about 棚卸資産, there are

• FIFO
• Individual, user needs to specify each
• weighted average (総平均法)
• moving average (移動平均法)

(Others I'm not sold to support)

Explicitness

Another difficulty is the clarity. We should write it back to the original file so that we can have a explicit understanding.

Ambiguous "income"

It's trivial if the commodity is always bought with the certain currency and sold on the same one. But it's more hard to tell if the transaction has profit or not for multi-currency case.