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56 lines
1.1 KiB
Go
56 lines
1.1 KiB
Go
package either
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import "fmt"
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type EitherTag int
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const (
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LeftTag EitherTag = iota
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RightTag
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)
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// Either defines a data structure that logically holds either an E or an A. The tag discriminates the cases
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type Either[E, A any] struct {
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Tag EitherTag
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Left E
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Right A
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}
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// String prints some debug info for the object
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func (s Either[E, A]) String() string {
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switch s.Tag {
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case LeftTag:
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return fmt.Sprintf("Left[%T, %T](%v)", s.Left, s.Right, s.Left)
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case RightTag:
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return fmt.Sprintf("Right[%T, %T](%v)", s.Left, s.Right, s.Right)
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}
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return "Invalid"
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}
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func IsLeft[E, A any](val Either[E, A]) bool {
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return val.Tag == LeftTag
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}
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func IsRight[E, A any](val Either[E, A]) bool {
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return val.Tag == RightTag
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}
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func Left[E, A any](value E) Either[E, A] {
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return Either[E, A]{Tag: LeftTag, Left: value}
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}
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func Right[E, A any](value A) Either[E, A] {
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return Either[E, A]{Tag: RightTag, Right: value}
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}
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func fold[E, A, B any](ma Either[E, A], onLeft func(e E) B, onRight func(a A) B) B {
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if IsLeft(ma) {
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return onLeft(ma.Left)
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}
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return onRight(ma.Right)
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}
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func Unwrap[E, A any](ma Either[E, A]) (A, E) {
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return ma.Right, ma.Left
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}
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