Round amount with strategies

Questions
,
1

Hi community,

Could you help me to understand if somehow it’s possible to have different strategies for example to round a value.
I leave you the example bellow to be easier to understand what I would like to do. In this example each company
can create a Product contract which applies a round “strategy” to Subscription amount, according with each company preferences.

For example in Product 1, released by company 1, they want to use floor “strategy” to round amounts,
but company 2 wants to use ceil “strategy” to round amounts.

That’s I would like to implement with roundAmount function.
Somehow pass the strategy name and grab its corresponding fn in a dynamic way.
Is it possible to have it using DAML ? For example with a Map Text FN ? Or using another ways ?

template Product
    with
        code: Text
        round_strategy: Text
        issuer: Party
    where
        signatory issuer
    
        controller issuer can
           nonconsuming Product_Propose_Subscription : ContractId SubscriptionProposal
                with
                    holder: Party
                    amount_quote: Decimal
                do
                    create SubscriptionProposal with
                        code = "some bussiness code"
                        product_code = code
                        amount = roundAmount amount_quote round_strategy
                        issuer
                        holder


template SubscriptionProposal
    with
        code: Text
        product_code: Text
        amount: Int
        issuer: Party
        holder: Party
    where
        signatory issuer



roundAmount: Decimal -> Text -> Int
roundAmount amount strategy = 
    let strategyFn = getRoundStrategyFn strategy
    strategyFn amount
2

If you know of all of the strategies in advance (i.e. at template definition time), you can have a simple enum on the wire and use that.

If you want a more open-ended set of options, you’ll need to invent your own mini-language and write an interpreter for it in Daml. It’s not very difficult (if you keep to an abstract syntax and skip over all the parsing stuff) for a simple arithmetic language. See this post for a more in-depth example.

Edit: This discussion may also be relevant.

3

@Gary_Verhaegen Thank you for you suggestions. I believe this enum approach will do.