bql subtract Amounts?

[Ben L]

Is there a way to subtract Amounts (same currency) in bql? 

select cost(position) - value(position);

I get:

TypeError: unsupported operand type(s) for -: 'Amount' and 'Amount'

I can structure the query so the results are only one currency. Is there a function that will report an Amount as just a number (lose the currency)? 

Thanks,

Ben

[Martin Blais]

I don't think it's supported; you can try adding it (in branch master), should be easy, just check the currencies match

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[Ben L]

Happy to take a stab at it if you want to point where it look. I can't find where in the beancount code to start. Since the error raised is TypeError,  I searched that and for the "unsupported operand" error, but I can't find that in the code. Can you point me to where does the bql stuff for math (add, subtract, etc) get handled?

Thanks,

[redst...@gmail.com]

I would start with this line:

class EvalSub(EvalBinaryOp):

 def __init__(self, left, right):
   f = lambda x, y: Decimal(x - y)

   super().__init__(f, left, right, Decimal)

It's in query_compile.py:210. I'd imagine subtraction done via Decimal should instead be modified to handle your case. Tests are here.

"unsupported operand type(s) for -:" is a python TypeError (not specific to Beancount), which is why you didn't find it in the code. I did "git grep operand" to find the above.

This would be a good addition, BTW. Thanks for taking a stab at it!

[redst...@gmail.com]

See this comment right above those lines from Martin. Would be great to do get both these working if you're up for it :)

# Note: We ought to implement implicit type promotion here,
# e.g., int -> float -> Decimal.

# Note(2): This does not support multiplication on Amount, Position, Inventory.
# We need to rewrite the evaluator to support types in order to do this
# properly.

[Ben L]

The changes I made were pretty minor and leveraged existing code for adding  / subtracting Amounts. See https://github.com/beancount/beancount/pull/688 and let me know what you think, etc.

[Martin Blais]

Sorry just catching up on that thread.

I've been meaning to delete the beanquery from beancount/master and start using the beanquery repo.

To be fair, I haven't been able to switch over yet; I just added it to my environment, it works.

I should probably delete beancount/beancount/query

Not sure how to proceed yet, maybe this weekend there's time

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