Support simple arithmetic expressions in posting amounts

[purpleidea]

It would be useful if posting amounts could contain simple arithmetic expressions, for example:

assets:personal    $-21.60 + $-27.68 + $-5.03 + $-17.80

Currently this fails with unexpected '+', requiring the user to calculate and enter $-72.11 manually.

Supporting basic +, -, *, /, and parentheses in posting amounts would make journal entries easier to audit because the original component amounts could remain visible.

This would be incredibly useful for situations when I have 5 receipts in a section where each is split into base amount (price+tip) and tax (as second line item) which is common in accounting where I live.

Seeing the total at the bottom would make it easier to find the bill. Eg:

2025-10-14 some outing		; customer:simon
	expenses:meals			$47.97 ; page:13
	assets:tax:gstexp		$2.23
	expenses:meals			$200.65 ; page:17
	assets:tax:gstexp		$8.35
	expenses:parking		$15.75 ; page:20
	assets:tax:gstexp		$0.79
	expenses:lodging		$419.32 ; page:21
	assets:tax:gstexp		$18.68
	assets:personal			$-50.20 + $-209.00 + $-16.54 + $-438   ; $-713.74

Thank you!

[simonmichael]

PR #934 is the closest we've come to supporting this. I don't think it's a vital feature but we would accept a good implementation. Other past discussion: #183, #871.

[purpleidea]

Gotcha thanks! Hopefully this is a bit simpler/clearer than the open issue, but feel free to keep this or close it as you wish. I don't think my haskell is strong enough at the moment to be able to tackle this, but I do think it's neat this is implemented in haskell!

I'd be willing to sponsor the work up to $400 CAD if it meets my expectations and yours. Someone is welcome to contact me in advance for such approval if interested. (My small open source company can't pay just any country.)

[RomeoApps]

James, I can take this on if Italy is an eligible payee country for your sponsor.

I propose a fixed CAD 400 milestone on current main: arithmetic expressions in posting amounts with +, -, *, /, precedence and parentheses; preservation of existing commodity/default-commodity and cost/lot syntax; deterministic errors for divide-by-zero and invalid commodity combinations; parser and functional coverage; and current journal documentation. I reviewed #183, #871, #934 and #913, and would start docs-first to keep the semantics and support burden explicit.

I would keep exact balance assertions and broad multi-commodity expression work out of this milestone unless you and Simon confirm #2648 requires them. Please confirm:

1. Italy is an eligible payee country;
2. this acceptance boundary;
3. CAD 400 fixed price.

After written approval, I will create one dedicated CAD Stripe checkout and begin only after payment is verified.

Romeo
romeoapps.com

[purpleidea]

@RomeoApps I can only pay you after @simonmichael approves and merges the commit. I'll also need an invoice with a small document signed that shows I own the work I'm paying for (will provide). I can go up to $450 CAD even. I can't pay in advance, but I think if you look me up reputationally, you don't need to worry that I'm not good for it.

[purpleidea]

@simonmichael I will also add on $50 CAD to your side for review if it's not a hassle to send an invoice for such a small amount. I'm sorry it's not a lot, just a small open source company for now, but trying to build with the right principles.

[RomeoApps]

Thanks, James. A fixed CAD 450 total, invoiced after maintainer approval and merge, is workable in principle subject to the conditions below.

Please confirm that an Italy-based contractor is eligible, the intended payment route, currency/fee handling, and whether the invoice is due on receipt. Please also send the ownership document for review before implementation; it must be limited to this contribution and preserve hledger's GPL-3 licensing. I cannot pre-accept broader IP, indemnity, warranty, confidentiality, or unrelated obligations.

@simonmichael, if the single-commodity posting-expression scope above is acceptable in principle and RomeoApps may proceed, could you confirm the design/acceptance direction? I will wait for that written go-ahead and the terms above before implementation.

Romeo / romeoapps.com

[purpleidea]

Please confirm that an Italy-based contractor is eligible

Not a problem.

the intended payment route, currency/fee handling

Can send direct wire transfer to your bank or pay by credit card to whatever if you prefer. I pay to send the wire transfer on my side, any receiving fees are your business.

and whether the invoice is due on receipt.

After merged, I'll pay within 30 days of receiving a valid invoice.

Please also send the ownership document for review before implementation; it must be limited to this contribution and preserve hledger's GPL-3 licensing. I cannot pre-accept broader IP, indemnity, warranty, confidentiality, or unrelated obligations.

Nah, simple 1 pager CLA that says I own the copyright of the work produced, otherwise auditors would cause me trouble. I obviously plan to release the work under GPLv3+.

Cheers

[RomeoApps]

Thanks, James. For the fixed CAD 450 total, credit-card payment via a Stripe invoice after merge, payable within 30 days of a valid invoice, works in principle. Please send the one-page copyright document before implementation; it must be limited to this contribution and expressly authorize its submission and licensing in hledger under GPLv3+ without broader obligations. I’ll wait for that document and the maintainer’s explicit confirmation of the proposed single-commodity scope and go-ahead before starting.

[simonmichael]

@purpleidea, thanks for offering a substantial bounty. @RomeoApps, thanks for your interest.

In the AI age we/I have to be careful to conserve maintainer time, avoid burnout, avoid low quality or destabilising contributions, etc. A few notes:

• The RomeoApps account is a few weeks old and likely heavily AI-assisted.

• To be eligible for merging in the official hledger repo, PRs need to follow the latest https://hledger.org/PULLREQUESTS.html#guidelines and https://hledger.org/AI.html#rules-of-engagement.

• purpleidea if you have additional AI preferences, you may want to mention them up front.

• This bounty is being offered and managed by purpleidea, with little involvement from me except in deciding whether to merge the result. I hope that will happen, but there's no promise of that. Of course the work can be useful even if not merged; that is the beauty of FOSS.

Good luck!

[simonmichael]

• With the open discussion of a bounty, this issue will soon attract more automated queries, PRs and bounty claims. These will keep coming until it's closed, and will also need to be managed.