Accumulator factory

editable example

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ghul

use IO.Std.write_line

union Number is

WHOLE(value: int)

FRACTIONAL(value: double)

si

use Number.WHOLE

use Number.FRACTIONAL

widen(n: Number) -> double =>

case ►n

when (value): WHOLE then cast(value)

when (value): FRACTIONAL then value

esac

add(left: Number, right: Number) -> Number =>

if let whole_left: WHOLE = ►left, whole_right: WHOLE = ►right then

WHOLE(whole_left.value + whole_right.value)

else

FRACTIONAL(widen(left) + widen(right))

fi

show(n: Number) -> string =>

case ►n

when (value): WHOLE then "{value}"

when (value): FRACTIONAL then "{value}"

esac

accumulator(initial: Number) -> Number -> Number is

let sum mut = initial

return value => (

sum = add(sum, value)

sum

)

si

let x = accumulator(WHOLE(1))

x(WHOLE(5))

accumulator(WHOLE(3))

write_line(show(x(FRACTIONAL(2.3D))))

let y = accumulator(WHOLE(10))

y(WHOLE(5))

write_line(show(y(WHOLE(5))))

8.3
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