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import {
Alternative as AL,
Applicative as AP,
SemiApplicative as SE,
} from '@effect/typeclass'
import {pipe} from 'effect'
import type {TypeLambda} from 'effect/HKT'
import {UnderlyingArbitrary} from '../../../arbitrary.js'
import type {BuildParameterized, ParameterizedGiven as Given} from './given.js'
import {unfoldGiven} from './given.js'
import {BuildInternal} from './internal.js'
import {semiAlternativeLaws} from './SemiAlternative.js'
/**
* Typeclass laws for `Alternative`.
* @category typeclass laws
*/
export const alternativeLaws: BuildParameterized<AlternativeTypeLambda> = (
given,
suffix?,
) =>
pipe(
buildLaws(`Alternative${suffix ?? ''}`, given),
pipe(given, semiAlternativeLaws, addLawSets),
)
const buildLaws: BuildInternal<AlternativeTypeLambda> = (name, given) => {
const unfolded = unfoldGiven(given),
{F, equalsFa, fa} = unfolded,
{coproduct, coproductAll} = F,
isApplicative = 'productAll' in F && 'of' in F
type A = UnderlyingArbitrary<(typeof unfolded)['a']>
return lawTests(
name,
Law(
'left identity',
'∅ ⊕ fa = fa',
fa,
)(fa => equalsFa(coproduct(fa, F.zero<A>()), fa)),
Law(
'right identity',
'fa ⊕ ∅ = fa',
fa,
)(fa => equalsFa(coproduct(F.zero<A>(), fa), fa)),
Law(
'coproductAll zero',
'coproductAll([]) = ∅',
fa,
)(() => equalsFa(coproductAll([]), F.zero<A>())),
...(isApplicative ? buildApplicativeLaws(given) : []),
)
}
// Extra laws for alternatives that have an applicative instance.
const buildApplicativeLaws = <
F extends TypeLambda,
A,
B = A,
C = A,
R = never,
O = unknown,
E = unknown,
>(
given: Given<AlternativeTypeLambda, F, A, B, C, R, O, E>,
) => {
const {F, equalsFb, fa, ab, fabOf} = unfoldGiven(given),
{coproduct, map} = F
const Ap = F as unknown as AP.Applicative<F>,
ap = SE.ap(Ap),
of = Ap.of,
fab = fabOf(of)
return [
Law(
'right absorption',
'ap(fab, ∅) = ∅',
fab,
)(fab => equalsFb(ap(fab, F.zero<A>()), F.zero<B>())),
Law(
'left distributivity',
'coproduct(fa₁, fa₂) ▹ map(ab) =' +
' coproduct(map(fa₁, ab), map(fa₂, ab))',
fa,
fa,
ab,
)((fa1, fa2, ab) =>
equalsFb(
pipe(coproduct(fa1, fa2), map(ab)),
coproduct(map(fa1, ab), map(fa2, ab)),
),
),
Law(
'right distributivity',
'coproduct(fab₁, fab₂) ▹ ap(fa) =' +
' coproduct(ap(fab₁, fa), ap(fab₂, fa))',
fa,
fab,
fab,
)((fa, fab1, fab2) =>
equalsFb(
pipe(coproduct(fab1, fab2), ap(fa)),
coproduct(ap(fab1, fa), ap(fab2, fa)),
),
),
]
}
/**
* Type lambda for the `Alternative` typeclass.
* @category type lambda
*/
export interface AlternativeTypeLambda extends TypeLambda {
readonly type: AL.Alternative<this['Target'] & TypeLambda>
}
declare module './given.js' {
interface ParameterizedLambdas {
Alternative: AlternativeTypeLambda
}
}
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