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chaining channels in go
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| package main | |
| import ( | |
| "unicode/utf8" | |
| ) | |
| type Item string | |
| type Stream chan Item | |
| type Acc string | |
| func NewWordStream(words []Item) Stream { | |
| stream := make(Stream) | |
| go func() { | |
| for _, w := range words { | |
| stream <- w | |
| } | |
| close(stream) | |
| }() | |
| return stream | |
| } | |
| func (in Stream) Map(fn func(Item) Item) Stream { | |
| out := make(Stream) | |
| go func() { | |
| for x := range in { | |
| out <- fn(x) | |
| } | |
| close(out) | |
| }() | |
| return out | |
| } | |
| func (in Stream) Filter(fn func(Item) bool) Stream { | |
| out := make(Stream) | |
| go func() { | |
| for x := range in { | |
| if fn(x) { | |
| out <- x | |
| } | |
| } | |
| close(out) | |
| }() | |
| return out | |
| } | |
| func (in Stream) Reduce(fn func(Acc, Item) (Acc, Acc)) chan Acc { | |
| out := make(chan Acc) | |
| go func() { | |
| var val, acc Acc | |
| for x := range in { | |
| acc, val = fn(acc, x) | |
| if val != "" { | |
| out <- val | |
| } | |
| } | |
| close(out) | |
| }() | |
| return out | |
| } | |
| func main() { | |
| reverse := func(word Item) Item { | |
| s := string(word) | |
| o := make([]rune, utf8.RuneCountInString(s)) | |
| i := len(o) | |
| for _, c := range s { | |
| i-- | |
| o[i] = c | |
| } | |
| return Item(o) | |
| } | |
| longerThan := func(n int) func(Item) bool { | |
| return func(w Item) bool { | |
| return len(w) > n | |
| } | |
| } | |
| not := func(s string) func(Item) bool { | |
| return func(w Item) bool { | |
| return s != string(w) | |
| } | |
| } | |
| words := []Item{"this", "is", "pretty", "cool"} | |
| stream :=NewWordStream(words).Map(reverse).Filter(longerThan(2)).Map(reverse).Filter(not("this")) | |
| for w := range stream { | |
| println(w) | |
| } | |
| } |
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