beancount

I’m not sure why I took so long to start using Github Copilot, but I’ve been completely whelmed by it so far. It sometimes saves entire seconds in my workflow! In contrast GPT-4 has induced more of those “wow” moments and saves me hours of work. That said, in practice Copilot works surprisingly well for Beancount ledger files. Not super intelligently. But it does work. Duplicating regular transactions from the same ledger file. The first major caveat is Copilot appears to only draw from the immediate file and doesn’t respect imports (and definitely doesn’t go up the ledger tree if you’re working in an imported file). If you have a semi-regular order from a restaurant it will parrot that entry perfectly. Mostly new transactions For entries it hasn’t seen before, Copilot does a good job at guessing the account names and memo from just the Payee. At restaurants I regularly use my Amex blue or Gift cards and expense the txn to Expenses:Business:Meals:Restaurants. Copilot is in the ballpark by guessing those (seemingly at random). Similarly, it correctly interprets that I use my Wells Fargo 2% card for unspecific purchases. This ledger has no previous reference to Home Depot, but it’s also a fair guess to expense that to Expenses:Personal:Home (which does exist). Obviously the amounts for new transactions are unknowable, but otherwise it’s dead on. The computer knows arithmetic? On “new” accounts, Copilot always suggests balance entries that are completely wrong. However it can correctly calculate between two balance statements even in my extremely crowded year ledgers. For example, my Assets:GiftCards:Amazon account has a balance of $0 on March 9th. I assert this with: 2023-03-09 balance Assets:GiftCards:Amazon 0 USD I then make a couple transactions on this gift card: $ bean-query ./money/ledger.beancount 'SELECT date, account, position, balance FROM OPEN ON 2023-03-11 WHERE account ~ "Assets:GiftCards:Amazon"' date account position balance ---------- ----------------------- ---------- --------- 2023-03-11 Assets:GiftCards:Amazon 42.25 USD 42.25 USD 2023-03-11 Assets:GiftCards:Amazon 21.74 USD 63.99 USD 2023-03-11 Assets:GiftCards:Amazon 29.04 USD 93.03 USD 2023-03-15 Assets:GiftCards:Amazon -24.12 USD 68.91 USD 2023-03-18 Assets:GiftCards:Amazon -17.45 USD 51.46 USD 2023-03-22 Assets:GiftCards:Amazon 2.56 USD 54.02 USD 2023-04-01 Assets:GiftCards:Amazon -51.32 USD 2.70 USD After those 7 transactions (and no other assertions) the card has a calculated balance of $2.70. Now on April 2nd I want to assert this balance. What does Copilot suggest? It does the math correctly!! It perfectly calculated a running total between the balance, all 7 transactions, and this new balance. Copilot gets completions wrong 75% of the time, but I find it so incredibly impressive when it’s right. Hallucinating As with all LLMs, the cracks start to show when your prompts suck. With less information it will just make up account names. While Assets:Banks:SF:Checking does exist those two sub accounts do not. Granted it doesn’t know that, since all my account declarations are in a separate file. It did correctly interpret my memo of “Withdraw $40 cash” by writing 40 USD as the amount. Another example: When completing a balance for an account I have never asserted before, it really starts to flail in the dark: I don’t have an Assets:Banks:Venmo:Checking account. I don’t have 1k in that non-existent account. My actual balance in the existing parent Assets:Banks:Venmo is a hot $3.43. I wonder if there’s a future in which PayPal bribes Microsoft to encourage beancounting Copilot users to make more Venmo $$$ deposits? Surely not… My Confidence While the specific account names and transaction amounts are more often wrong than right, in my opinion Copilot is still worth it for autocompleting the structure of entries. It cannot be trusted to get the details right. It only has a good grasp on what the ledger file should look like and how to nudge you there.

Thanks to /u/orcusvoyager1hampig for spelling this out to me on reddit I go out to dinner with a friend and they offer to pay me back later for their meal. I write this in my ledger: 2021-07-19 * "Chipotle" "Dinner w/Dave" Liabilities:AmEx:Blue -30 USD Assets:Debts:Dave 15 USD Expenses:Dining 15 USD This makes sense to me. Today, I sold something for Dave on ebay. I’m going to reduce what he owes me using that part of the payment: 2021-07-30 * "ebay" "payment" Assets:Bank 25 USD Income:Ebay -20 USD ; my stuff Income:Ebay -5 USD ; Dave's $5 item Assets:Debts:Dave -5 USD ; ???? This does not balance. As a quick fix, I can remove the Income:Ebay -5 USD and take that from Dave’s debt account directly. However, at the end of the month beancount will report $20 of revenue while ebay’s statement will report the full $25. Matching these numbers is important to me. What I need to do is: Keep a record of Assets:Inventory as an intermediary between Dave’s debt and my other Assets. Keep a record of Expenses:COGS (Cost Of Goods Sold) to sink Dave’s transferred inventory into once sold. Note the additional transaction here: 2021-07-19 * "Chipotle" "Dinner w/Dave" Liabilities:AmEx:Blue -30 USD Assets:Debts:Dave 15 USD Expenses:Dining 15 USD ; ; Dave's debt is officially reduced here: ; 2021-07-30 * "Dave gives me his things to sell" Assets:Inventory 5 USD Assets:Debts:Dave 2021-07-30 * "ebay" "payment ; sold $20 of my things and $5 of dave's" Assets:Bank 25 USD Income:Ebay -25 USD ; my stuff + Dave's $5 item Assets:Inventory -5 USD Expenses:COGS 5 USD For future debts I will need to determine the price of our asset transaction ($5) after the item is sold. Quick dose of nostalgia, when googling beancount COGS, a wiki for Toontown is the first result. Fun times. Interesting plugin for deeper Fava integration: https://github.com/ROCHK/fava_inventory