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discard """ | ||
output: ''' | ||
true | ||
true | ||
true | ||
3 | ||
18.0 | ||
324.0 | ||
''' | ||
""" | ||
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type RNG = object | ||
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proc random(rng: var RNG): float = 1.0 | ||
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type | ||
RandomVar[A] = concept x | ||
var rng: RNG | ||
rng.sample(x) is A | ||
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Constant[A] = object | ||
value: A | ||
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Uniform = object | ||
a, b: float | ||
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ClosureVar[A] = proc(rng: var RNG): A | ||
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proc sample[A](rng: var RNG, c: Constant[A]): A = c.value | ||
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proc sample(rng: var RNG, u: Uniform): float = u.a + (u.b - u.a) * rng.random() | ||
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proc sample[A](rng: var RNG, c: ClosureVar[A]): A = c(rng) | ||
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proc constant[A](a: A): Constant[A] = Constant[A](value: a) | ||
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proc uniform(a, b: float): Uniform = Uniform(a: a, b: b) | ||
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proc lift1[A, B](f: proc(a: A): B, r: RandomVar[A]): ClosureVar[B] = | ||
proc inner(rng: var RNG): B = f(rng.sample(r)) | ||
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return inner | ||
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when isMainModule: | ||
proc sq(x: float): float = x * x | ||
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let | ||
c = constant(3) | ||
u = uniform(2, 18) | ||
t = lift1(sq, u) | ||
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var rng: RNG | ||
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echo(c is RandomVar[int]) | ||
echo(u is RandomVar[float]) | ||
echo(t is RandomVar[float]) | ||
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echo rng.sample(c) | ||
echo rng.sample(u) | ||
echo rng.sample(t) | ||
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