add ranger

ranger/range.go

@@ -0,0 +1,84 @@
+package main
+
+// export GOEXPERIMENT=rangefunc
+import "iter"
+
+func Step(start, stop, step int) iter.Seq[int] {
+	if step < 0 {
+		return func(yield func(int) bool) {
+			for i := start; i <= start && i > stop; i += step {
+				next := yield(i)
+				if !next {
+					return
+				}
+			}
+		}
+	}
+
+	if step > 0 {
+		return func(yield func(int) bool) {
+			for i := start; i >= start && i < stop; i += step {
+				next := yield(i)
+				if !next {
+					println("stopped!")
+					return
+				}
+			}
+		}
+	}
+
+	return func(yield func(int) bool) { yield(start) }
+}
+
+func Fib() iter.Seq[uint] {
+	return func(yield func(uint) bool) {
+		previous, value := uint(1), uint(1)
+		next := yield(value)
+		for next {
+			next = yield(value)
+			value, previous = value+previous, value
+			if value < previous {
+				return
+			}
+		}
+	}
+}
+
+func Fizzbuzzed[T int | uint](from iter.Seq[T]) iter.Seq2[T, string] {
+	pull, stop := iter.Pull(from)
+	return func(yield func(T, string) bool) {
+		defer stop()
+		for {
+			var fizzbuzz string
+			p, ok := pull()
+			if !ok {
+				return
+			}
+			if p%3 == 0 {
+				fizzbuzz = "fizz"
+			}
+			if p%5 == 0 {
+				fizzbuzz += "buzz"
+			}
+			if !yield(p, fizzbuzz) {
+				return
+			}
+		}
+	}
+}
+
+// func main() {
+// 	for i, v := range Fizzbuzzed(Fib()) {
+// 		println(i, v)
+// 	}
+// }
+
+func countScan(n int) (func() bool, func() int) {
+	pos := -1
+	return func() bool {
+			pos++
+			return pos < n
+		}, func() int {
+			return pos
+		}
+}