Golang Dec.SetString方法代码示例

func TestDecGobEncoding(t *testing.T) {
	var medium bytes.Buffer
	enc := gob.NewEncoder(&medium)
	dec := gob.NewDecoder(&medium)
	for i, test := range decGobEncodingTests {
		for j := 0; j < 2; j++ {
			for k := inf.Scale(-5); k <= 5; k++ {
				medium.Reset() // empty buffer for each test case (in case of failures)
				stest := test
				if j != 0 {
					// negative numbers
					stest = "-" + test
				}
				var tx inf.Dec
				tx.SetString(stest)
				tx.SetScale(k) // test with positive, negative, and zero scale
				if err := enc.Encode(&tx); err != nil {
					t.Errorf("#%d%c: encoding failed: %s", i, 'a'+j, err)
				}
				var rx inf.Dec
				if err := dec.Decode(&rx); err != nil {
					t.Errorf("#%d%c: decoding failed: %s", i, 'a'+j, err)
				}
				if rx.Cmp(&tx) != 0 {
					t.Errorf("#%d%c: transmission failed: got %s want %s", i, 'a'+j, &rx, &tx)
				}
			}
		}
	}
}

// ParseQuantity turns str into a Quantity, or returns an error.
func ParseQuantity(str string) (*Quantity, error) {
	parts := splitRE.FindStringSubmatch(strings.TrimSpace(str))
	// regexp returns are entire match, followed by an entry for each () section.
	if len(parts) != 3 {
		return nil, ErrFormatWrong
	}

	amount := new(inf.Dec)
	if _, ok := amount.SetString(parts[1]); !ok {
		return nil, ErrNumeric
	}

	base, exponent, format, ok := quantitySuffixer.interpret(suffix(parts[2]))
	if !ok {
		return nil, ErrSuffix
	}

	// So that no one but us has to think about suffixes, remove it.
	if base == 10 {
		amount.SetScale(amount.Scale() + inf.Scale(-exponent))
	} else if base == 2 {
		// numericSuffix = 2 ** exponent
		numericSuffix := big.NewInt(1).Lsh(bigOne, uint(exponent))
		ub := amount.UnscaledBig()
		amount.SetUnscaledBig(ub.Mul(ub, numericSuffix))
	}

	// Cap at min/max bounds.
	sign := amount.Sign()
	if sign == -1 {
		amount.Neg(amount)
	}
	// This rounds non-zero values up to the minimum representable
	// value, under the theory that if you want some resources, you
	// should get some resources, even if you asked for way too small
	// of an amount.
	// Arguably, this should be inf.RoundHalfUp (normal rounding), but
	// that would have the side effect of rounding values < .5m to zero.
	amount.Round(amount, 3, inf.RoundUp)

	// The max is just a simple cap.
	if amount.Cmp(maxAllowed) > 0 {
		amount.Set(maxAllowed)
	}
	if format == BinarySI && amount.Cmp(decOne) < 0 && amount.Cmp(decZero) > 0 {
		// This avoids rounding and hopefully confusion, too.
		format = DecimalSI
	}
	if sign == -1 {
		amount.Neg(amount)
	}

	return &Quantity{amount, format}, nil
}

func TestDecSetString(t *testing.T) {
	tmp := new(inf.Dec)
	for i, test := range decStringTests {
		if test.scale < 0 {
			// SetString only supports scale >= 0
			continue
		}
		// initialize to a non-zero value so that issues with parsing
		// 0 are detected
		tmp.Set(inf.NewDec(1234567890, 123))
		n1, ok1 := new(inf.Dec).SetString(test.in)
		n2, ok2 := tmp.SetString(test.in)
		expected := inf.NewDec(test.val, test.scale)
		if ok1 != test.ok || ok2 != test.ok {
			t.Errorf("#%d (input '%s') ok incorrect (should be %t)", i, test.in, test.ok)
			continue
		}
		if !ok1 {
			if n1 != nil {
				t.Errorf("#%d (input '%s') n1 != nil", i, test.in)
			}
			continue
		}
		if !ok2 {
			if n2 != nil {
				t.Errorf("#%d (input '%s') n2 != nil", i, test.in)
			}
			continue
		}

		if n1.Cmp(expected) != 0 {
			t.Errorf("#%d (input '%s') got: %s want: %d", i, test.in, n1, test.val)
		}
		if n2.Cmp(expected) != 0 {
			t.Errorf("#%d (input '%s') got: %s want: %d", i, test.in, n2, test.val)
		}
	}
}

func ExampleDec_SetString() {
	d := new(inf.Dec)
	d.SetString("012345.67890") // decimal; leading 0 ignored; trailing 0 kept
	fmt.Println(d)
	// Output: 12345.67890
}