func (a *Mpint) SetFloat(b *Mpflt) int { // avoid converting huge floating-point numbers to integers // (2*Mpprec is large enough to permit all tests to pass) if b.Val.MantExp(nil) > 2*Mpprec { return -1 } if _, acc := b.Val.Int(&a.Val); acc == big.Exact { return 0 } const delta = 16 // a reasonably small number of bits > 0 var t big.Float t.SetPrec(Mpprec - delta) // try rounding down a little t.SetMode(big.ToZero) t.Set(&b.Val) if _, acc := t.Int(&a.Val); acc == big.Exact { return 0 } // try rounding up a little t.SetMode(big.AwayFromZero) t.Set(&b.Val) if _, acc := t.Int(&a.Val); acc == big.Exact { return 0 } return -1 }
func ExampleFloat_Add() { // Operating on numbers of different precision. var x, y, z big.Float x.SetInt64(1000) // x is automatically set to 64bit precision y.SetFloat64(2.718281828) // y is automatically set to 53bit precision z.SetPrec(32) z.Add(&x, &y) fmt.Printf("x = %.10g (%s, prec = %d, acc = %s)\n", &x, x.Text('p', 0), x.Prec(), x.Acc()) fmt.Printf("y = %.10g (%s, prec = %d, acc = %s)\n", &y, y.Text('p', 0), y.Prec(), y.Acc()) fmt.Printf("z = %.10g (%s, prec = %d, acc = %s)\n", &z, z.Text('p', 0), z.Prec(), z.Acc()) // Output: // x = 1000 (0x.fap+10, prec = 64, acc = Exact) // y = 2.718281828 (0x.adf85458248cd8p+2, prec = 53, acc = Exact) // z = 1002.718282 (0x.faadf854p+10, prec = 32, acc = Below) }