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|
(.require
[library
[lux (.except)
[abstract
["[0]" equivalence (.only Equivalence)]]
[data
["[0]" product]
["[0]" text (.only)
["%" \\format]]]
[math
[number
["n" nat]]]
[meta
["[0]" static]
[type
["[0]" nominal]]]]]
[/
["/" currency]])
(nominal.def .public (Money currency)
(Record
[#currency (/.Currency currency)
#amount Nat])
(def .public (money currency amount)
(All (_ currency)
(-> (/.Currency currency) Nat
(Money currency)))
(nominal.abstraction
[#currency currency
#amount amount]))
(with_template [<name> <slot> <type>]
[(def .public <name>
(All (_ currency)
(-> (Money currency)
<type>))
(|>> nominal.representation
(the <slot>)))]
[currency #currency (/.Currency currency)]
[amount #amount Nat]
)
(def .public equivalence
(All (_ of)
(Equivalence (Money of)))
(at equivalence.functor each
(|>> nominal.representation)
(all product.equivalence
/.equivalence
n.equivalence
)))
(def .public (+ parameter subject)
(All (_ currency)
(-> (Money currency) (Money currency)
(Money currency)))
(|> subject
nominal.representation
(revised #amount (n.+ (|> parameter nominal.representation (the #amount))))
nominal.abstraction))
(def .public (- parameter subject)
(All (_ currency)
(-> (Money currency) (Money currency)
(Maybe (Money currency))))
(let [parameter (nominal.representation parameter)
subject (nominal.representation subject)]
(if (n.< (the #amount parameter)
(the #amount subject))
{.#None}
{.#Some (nominal.abstraction
[#currency (the #currency subject)
#amount (n.- (the #amount parameter)
(the #amount subject))])})))
(def .public (format it)
(All (_ currency)
(%.Format (Money currency)))
(let [[currency amount] (nominal.representation it)
[macro micro] (n./% (/.subdivisions currency) amount)]
(%.format (%.nat macro)
(when micro
0 ""
_ (%.format "." (%.nat micro)))
" " (/.alphabetic_code currency))))
)
|
