ml
108 lines
2.3 KiB
Go
108 lines
2.3 KiB
Go
package values
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// Unifier can be used to verify whether a list of values has equal entries.
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type Unifier struct {
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state unifierState
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}
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// NewUnifier returns a new instance.
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func NewUnifier() Unifier {
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return Unifier{state: unifierInitState{}}
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}
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// UnifierFor returns a unifier for a single value.
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func UnifierFor(value interface{}) Unifier {
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unifier := NewUnifier()
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unifier.Add(value)
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return unifier
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}
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// Add unifies the given value to the current state.
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// The given value must be comparable.
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func (u *Unifier) Add(value interface{}) {
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u.state = u.state.add(value)
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}
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// Unified returns the result of the unification.
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// If all values that were added to the unifier were equal, then the first
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// added value will be returned. Otherwise, nil will be returned.
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func (u *Unifier) Unified() interface{} {
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return u.state.unified()
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}
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// IsUnique returns true if the unifier has received only equal values.
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func (u Unifier) IsUnique() bool {
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return u.state.isUnique()
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}
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// IsEmpty returns true if the unifier has not received any value.
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func (u Unifier) IsEmpty() bool {
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return (u.state == nil) || u.state.isEmpty()
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}
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type unifierState interface {
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add(value interface{}) unifierState
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unified() interface{}
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isUnique() bool
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isEmpty() bool
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}
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type unifierInitState struct{}
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func (state unifierInitState) add(value interface{}) unifierState {
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return unifierMatchedState{value: value}
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}
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func (state unifierInitState) unified() interface{} {
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return nil
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}
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func (state unifierInitState) isUnique() bool {
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return false
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}
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func (state unifierInitState) isEmpty() bool {
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return true
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}
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type unifierMatchedState struct {
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value interface{}
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}
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func (state unifierMatchedState) add(value interface{}) unifierState {
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if state.value == value {
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return state
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}
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return unifierMismatchedState{}
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}
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func (state unifierMatchedState) unified() interface{} {
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return state.value
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}
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func (state unifierMatchedState) isUnique() bool {
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return true
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}
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func (state unifierMatchedState) isEmpty() bool {
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return false
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}
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type unifierMismatchedState struct{}
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func (state unifierMismatchedState) add(value interface{}) unifierState {
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return state
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}
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func (state unifierMismatchedState) unified() interface{} {
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return nil
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}
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func (state unifierMismatchedState) isUnique() bool {
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return false
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}
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func (state unifierMismatchedState) isEmpty() bool {
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return false
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}
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