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84 lines
1.8 KiB
Go
84 lines
1.8 KiB
Go
package merge
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import (
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"testing"
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)
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// additive implements an additive merge. Merging the two numbers together adds
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// the source value into the receiver without changing the source value.
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type additive struct {
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total int
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}
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func (a *additive) Merge(b *additive) error {
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a.total += b.total
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return nil
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}
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func (*additive) MergeIdentity() *additive { return new(additive) }
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func add(n int) *additive {
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return &additive{total: n}
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}
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type multiplicative struct {
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scale int
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}
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func (*multiplicative) MergeIdentity() *multiplicative { return &multiplicative{scale: 1} }
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func (m *multiplicative) Merge(v *multiplicative) error {
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m.scale *= v.scale
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return nil
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}
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func mul(n int) *multiplicative {
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return &multiplicative{scale: n}
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}
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// exclusive implements an exlsive merge. Merging the two numbers together adds
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// the value from the source into the destination, removing it from the source.
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type exclusive struct {
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stock int
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}
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func (e *exclusive) Merge(source *exclusive) error {
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e.stock += source.stock
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source.stock = 0
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return nil
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}
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func (*exclusive) MergeIdentity() *exclusive { return new(exclusive) }
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func ex(n int) *exclusive {
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return &exclusive{stock: n}
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}
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func TestMerge(t *testing.T) {
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t.Run("additive", func(t *testing.T) {
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a, b := add(4), add(7)
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if err := Merge(a, b); err != nil {
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t.Errorf("merge error: %v", err)
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}
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if a.total != 11 {
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t.Errorf("merge failed to mutate destination")
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}
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if b.total != 7 {
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t.Errorf("merged caused unexpected mutation")
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}
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})
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t.Run("exclusive", func(t *testing.T) {
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a, b := ex(4), ex(7)
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if err := Merge(a, b); err != nil {
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t.Errorf("merge error: %v", err)
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}
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if a.stock != 11 {
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t.Errorf("merge failed to mutate destination")
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}
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if b.stock != 0 {
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t.Errorf("merge failed to mutate source")
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}
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})
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}
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