示例#1
0
// This example demonstrates how to use big.Int to compute the smallest
// Fibonacci number with 100 decimal digits and to test whether it is prime.
func Example_fibonacci() {
	// Initialize two big ints with the first two numbers in the sequence.
	a := big.NewInt(0)
	b := big.NewInt(1)

	// Initialize limit as 10^99, the smallest integer with 100 digits.
	var limit big.Int
	limit.Exp(big.NewInt(10), big.NewInt(99), nil)

	// Loop while a is smaller than 1e100.
	for a.Cmp(&limit) < 0 {
		// Compute the next Fibonacci number, storing it in a.
		a.Add(a, b)
		// Swap a and b so that b is the next number in the sequence.
		a, b = b, a
	}
	fmt.Println(a) // 100-digit Fibonacci number

	// Test a for primality.
	// (ProbablyPrimes' argument sets the number of Miller-Rabin
	// rounds to be performed. 20 is a good value.)
	fmt.Println(a.ProbablyPrime(20))

	// Output:
	// 1344719667586153181419716641724567886890850696275767987106294472017884974410332069524504824747437757
	// false
}
示例#2
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func bignodes() {
	if bignodes_did {
		return
	}
	bignodes_did = true

	var i big.Int
	i.SetInt64(1)
	i.Lsh(&i, 63)

	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
	bigi.SetBigInt(&i)

	bigi.Convconst(&bigf, gc.Types[gc.TFLOAT64])
}
示例#3
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func (p *importer) float(x *Mpflt) {
	sign := p.int()
	if sign == 0 {
		x.SetFloat64(0)
		return
	}

	exp := p.int()
	mant := new(big.Int).SetBytes([]byte(p.string()))

	m := x.Val.SetInt(mant)
	m.SetMantExp(m, exp-mant.BitLen())
	if sign < 0 {
		m.Neg(m)
	}
}
示例#4
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func bignodes() {
	if bignodes_did {
		return
	}
	bignodes_did = true

	gc.Nodconst(&zerof, gc.Types[gc.TINT64], 0)
	zerof.Convconst(&zerof, gc.Types[gc.TFLOAT64])

	var i big.Int
	i.SetInt64(1)
	i.Lsh(&i, 63)
	var bigi gc.Node

	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
	bigi.SetBigInt(&i)
	bigi.Convconst(&two63f, gc.Types[gc.TFLOAT64])

	gc.Nodconst(&bigi, gc.Types[gc.TUINT64], 0)
	i.Lsh(&i, 1)
	bigi.SetBigInt(&i)
	bigi.Convconst(&two64f, gc.Types[gc.TFLOAT64])
}
示例#5
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func ExampleInt_SetString() {
	i := new(big.Int)
	i.SetString("644", 8) // octal
	fmt.Println(i)
	// Output: 420
}