106 lines
2.0 KiB
Go
106 lines
2.0 KiB
Go
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package iter
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type groupBy struct {
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curKey interface{}
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curKeyOk bool
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curValue interface{}
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keyFunc func(interface{}) interface{}
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input Iterator
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groupKey interface{}
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groupKeyOk bool
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}
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type Group interface {
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Iterator
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Key() interface{}
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}
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type group struct {
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gb *groupBy
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key interface{}
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first bool
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stopped bool
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}
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func (me *group) Stop() {
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me.stopped = true
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}
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func (me *group) Next() (ok bool) {
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if me.stopped {
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return false
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}
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if me.first {
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me.first = false
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return true
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}
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me.gb.advance()
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if !me.gb.curKeyOk || me.gb.curKey != me.key {
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me.Stop()
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return
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}
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ok = true
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return
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}
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func (me group) Value() (ret interface{}) {
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if me.stopped {
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panic("iterator stopped")
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}
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ret = me.gb.curValue
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return
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}
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func (me group) Key() interface{} {
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return me.key
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}
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func (me *groupBy) advance() {
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me.curKeyOk = me.input.Next()
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if me.curKeyOk {
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me.curValue = me.input.Value()
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me.curKey = me.keyFunc(me.curValue)
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}
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}
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func (me *groupBy) Next() (ok bool) {
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for me.curKey == me.groupKey {
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ok = me.input.Next()
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if !ok {
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return
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}
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me.curValue = me.input.Value()
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me.curKey = me.keyFunc(me.curValue)
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me.curKeyOk = true
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}
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me.groupKey = me.curKey
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me.groupKeyOk = true
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return true
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}
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func (me *groupBy) Value() (ret interface{}) {
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return &group{me, me.groupKey, true, false}
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}
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func (me *groupBy) Stop() {
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}
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// Allows use of nil as a return from the key func.
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var uniqueKey = new(int)
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// Group by returns an iterator of iterators over the values of the input
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// iterator that consecutively return the same value when input to the key
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// function. Note that repeated calls to each value of the GroupBy Iterator
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// does not return a new iterator over the values for that key.
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func GroupBy(input Iterator, keyFunc func(interface{}) interface{}) Iterator {
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if keyFunc == nil {
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keyFunc = func(a interface{}) interface{} { return a }
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}
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return &groupBy{
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input: input,
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keyFunc: keyFunc,
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groupKey: uniqueKey,
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curKey: uniqueKey,
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}
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}
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