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Implement RoundUp and RoundDown methods (#196)
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* Implement RoundUp and RoundDown methods
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@mwoss
mwoss committed Dec 11, 2020
1 parent 66332b3 commit 8bd41ac
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Showing 2 changed files with 222 additions and 2 deletions.
42 changes: 42 additions & 0 deletions decimal.go
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Expand Up @@ -870,6 +870,48 @@ func (d Decimal) Round(places int32) Decimal {
return ret
}

// RoundUp rounds the decimal towards +infinity.
//
// Example:
//
// NewFromFloat(545).RoundUp(-2).String() // output: "600"
// NewFromFloat(1.1001).RoundUp(2).String() // output: "1.11"
// NewFromFloat(-1.454).RoundUp(1).String() // output: "-1.4"
//
func (d Decimal) RoundUp(places int32) Decimal {
if d.exp >= -places {
return d
}

rescaled := d.rescale(-places)
if d.value.Sign() > 0 {
rescaled.value.Add(rescaled.value, oneInt)
}

return rescaled
}

// RoundDown rounds the decimal towards -infinity.
//
// Example:
//
// NewFromFloat(545).RoundDown(-2).String() // output: "500"
// NewFromFloat(1.1001).RoundDown(2).String() // output: "1.1"
// NewFromFloat(-1.454).RoundDown(1).String() // output: "-1.5"
//
func (d Decimal) RoundDown(places int32) Decimal {
if d.exp >= -places {
return d
}

rescaled := d.rescale(-places)
if d.value.Sign() < 0 {
rescaled.value.Sub(rescaled.value, oneInt)
}

return rescaled
}

// RoundBank rounds the decimal to places decimal places.
// If the final digit to round is equidistant from the nearest two integers the
// rounded value is taken as the even number
Expand Down
182 changes: 180 additions & 2 deletions decimal_test.go
View file
Expand Up @@ -968,13 +968,13 @@ func TestDecimal_RoundAndStringFixed(t *testing.T) {
for _, test := range tests {
d, err := NewFromString(test.input)
if err != nil {
panic(err)
t.Fatal(err)
}

// test Round
expected, err := NewFromString(test.expected)
if err != nil {
panic(err)
t.Fatal(err)
}
got := d.Round(test.places)
if !got.Equal(expected) {
Expand All @@ -994,6 +994,184 @@ func TestDecimal_RoundAndStringFixed(t *testing.T) {
}
}

func TestDecimal_RoundUpAndStringFixed(t *testing.T) {
type testData struct {
input string
places int32
expected string
expectedFixed string
}
tests := []testData{
{"1.454", 0, "2", ""},
{"1.454", 1, "1.5", ""},
{"1.454", 2, "1.46", ""},
{"1.454", 3, "1.454", ""},
{"1.454", 4, "1.454", "1.4540"},
{"1.454", 5, "1.454", "1.45400"},
{"1.554", 0, "2", ""},
{"1.554", 1, "1.6", ""},
{"1.554", 2, "1.56", ""},
{"0.554", 0, "1", ""},
{"0.454", 0, "1", ""},
{"0.454", 5, "0.454", "0.45400"},
{"0", 0, "0", ""},
{"0", 1, "0", "0.0"},
{"0", 2, "0", "0.00"},
{"0", -1, "0", ""},
{"5", 2, "5", "5.00"},
{"5", 1, "5", "5.0"},
{"5", 0, "5", ""},
{"500", 2, "500", "500.00"},
{"545", -1, "550", ""},
{"545", -2, "600", ""},
{"545", -3, "1000", ""},
{"545", -4, "10000", ""},
{"499", -3, "1000", ""},
{"499", -4, "10000", ""},
{"1.1001", 2, "1.11", ""},
{"-1.1001", 2, "-1.10", ""},
{"-1.454", 0, "-1", ""},
{"-1.454", 1, "-1.4", ""},
{"-1.454", 2, "-1.45", ""},
{"-1.454", 3, "-1.454", ""},
{"-1.454", 4, "-1.454", "-1.4540"},
{"-1.454", 5, "-1.454", "-1.45400"},
{"-1.554", 0, "-1", ""},
{"-1.554", 1, "-1.5", ""},
{"-1.554", 2, "-1.55", ""},
{"-0.554", 0, "0", ""},
{"-0.454", 0, "0", ""},
{"-0.454", 5, "-0.454", "-0.45400"},
{"-5", 2, "-5", "-5.00"},
{"-5", 1, "-5", "-5.0"},
{"-5", 0, "-5", ""},
{"-500", 2, "-500", "-500.00"},
{"-545", -1, "-540", ""},
{"-545", -2, "-500", ""},
{"-545", -3, "0", ""},
{"-545", -4, "0", ""},
{"-499", -3, "0", ""},
{"-499", -4, "0", ""},
}

for _, test := range tests {
d, err := NewFromString(test.input)
if err != nil {
t.Fatal(err)
}

// test Round
expected, err := NewFromString(test.expected)
if err != nil {
t.Fatal(err)
}
got := d.RoundUp(test.places)
if !got.Equal(expected) {
t.Errorf("Rounding up %s to %d places, got %s, expected %s",
d, test.places, got, expected)
}

// test StringFixed
if test.expectedFixed == "" {
test.expectedFixed = test.expected
}
gotStr := got.StringFixed(test.places)
if gotStr != test.expectedFixed {
t.Errorf("(%s).StringFixed(%d): got %s, expected %s",
d, test.places, gotStr, test.expectedFixed)
}
}
}

func TestDecimal_RoundDownAndStringFixed(t *testing.T) {
type testData struct {
input string
places int32
expected string
expectedFixed string
}
tests := []testData{
{"1.454", 0, "1", ""},
{"1.454", 1, "1.4", ""},
{"1.454", 2, "1.45", ""},
{"1.454", 3, "1.454", ""},
{"1.454", 4, "1.454", "1.4540"},
{"1.454", 5, "1.454", "1.45400"},
{"1.554", 0, "1", ""},
{"1.554", 1, "1.5", ""},
{"1.554", 2, "1.55", ""},
{"0.554", 0, "0", ""},
{"0.454", 0, "0", ""},
{"0.454", 5, "0.454", "0.45400"},
{"0", 0, "0", ""},
{"0", 1, "0", "0.0"},
{"0", 2, "0", "0.00"},
{"0", -1, "0", ""},
{"5", 2, "5", "5.00"},
{"5", 1, "5", "5.0"},
{"5", 0, "5", ""},
{"500", 2, "500", "500.00"},
{"545", -1, "540", ""},
{"545", -2, "500", ""},
{"545", -3, "0", ""},
{"545", -4, "0", ""},
{"499", -3, "0", ""},
{"499", -4, "0", ""},
{"1.1001", 2, "1.10", ""},
{"-1.1001", 2, "-1.11", ""},
{"-1.454", 0, "-2", ""},
{"-1.454", 1, "-1.5", ""},
{"-1.454", 2, "-1.46", ""},
{"-1.454", 3, "-1.454", ""},
{"-1.454", 4, "-1.454", "-1.4540"},
{"-1.454", 5, "-1.454", "-1.45400"},
{"-1.554", 0, "-2", ""},
{"-1.554", 1, "-1.6", ""},
{"-1.554", 2, "-1.56", ""},
{"-0.554", 0, "-1", ""},
{"-0.454", 0, "-1", ""},
{"-0.454", 5, "-0.454", "-0.45400"},
{"-5", 2, "-5", "-5.00"},
{"-5", 1, "-5", "-5.0"},
{"-5", 0, "-5", ""},
{"-500", 2, "-500", "-500.00"},
{"-545", -1, "-550", ""},
{"-545", -2, "-600", ""},
{"-545", -3, "-1000", ""},
{"-545", -4, "-10000", ""},
{"-499", -3, "-1000", ""},
{"-499", -4, "-10000", ""},
}

for _, test := range tests {
d, err := NewFromString(test.input)
if err != nil {
t.Fatal(err)
}

// test Round
expected, err := NewFromString(test.expected)
if err != nil {
t.Fatal(err)
}
got := d.RoundDown(test.places)
if !got.Equal(expected) {
t.Errorf("Rounding down %s to %d places, got %s, expected %s",
d, test.places, got, expected)
}

// test StringFixed
if test.expectedFixed == "" {
test.expectedFixed = test.expected
}
gotStr := got.StringFixed(test.places)
if gotStr != test.expectedFixed {
t.Errorf("(%s).StringFixed(%d): got %s, expected %s",
d, test.places, gotStr, test.expectedFixed)
}
}
}

func TestDecimal_BankRoundAndStringFixed(t *testing.T) {
type testData struct {
input string
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