72 lines
1.2 KiB
Go
72 lines
1.2 KiB
Go
// Package funky provides a few constructs usually present in pure
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// functional programming environments, using Go 1.18 generics.
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package funky
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// Maybe (sometimes called `Option`)
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type Maybe[V any] interface {
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IsNothing() bool
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Value() V
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}
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type maybe[V any] struct {
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isNothing bool
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value V
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}
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func Nothing[V any]() Maybe[V] {
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return &maybe[V]{isNothing: true}
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}
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func Just[V any](v V) Maybe[V] {
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return &maybe[V]{false, v}
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}
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func (m *maybe[V]) IsNothing() bool {
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return m.isNothing
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}
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func (m *maybe[V]) Value() V {
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return m.value
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}
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// Iterator
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type Iterator[V any] interface {
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Maybe[V]
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Next() Maybe[V]
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}
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type sliceIt[V any] struct {
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idx int
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slice []V
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}
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func SliceIterator[V any](sl []V) Iterator[V] {
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return &sliceIt[V]{slice: sl}
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}
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func (it *sliceIt[V]) Next() Maybe[V] {
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if it.IsNothing() {
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return Nothing[V]()
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}
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v := it.Value()
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it.idx++
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return Just(v)
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}
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func (it *sliceIt[V]) IsNothing() bool {
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return it.idx >= len(it.slice)
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}
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func (it *sliceIt[V]) Value() V {
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return it.slice[it.idx]
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}
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func Slice[V any](it Iterator[V]) []V {
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var out []V
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for m := it.Next(); !m.IsNothing(); m = it.Next() {
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out = append(out, m.Value())
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}
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return out
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}
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