iterators

ac15e18422ff69e6af398a72ce45a26ac945ef1f · ovidiucs · Feb 15, 2019 14:46
+65 · 1 file changed
iterating.nim +65 −0
diff --git a/iterating.nim b/iterating.nim
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+
+# Iterator have a function that returns multiple values
+# sequentially by calling the function repeatedly 
+
+iterator myFirstIterator(): int =
+    yield 111
+    yield 222
+    yield 333
+
+for n in myFirstIterator():
+    echo n
+
+iterator repeat[T](x: T): T=
+    while true:
+        yield x
+
+
+#for x in repeat("Hello World!"):
+#    echo x
+
+iterator countTo(x: int): int =
+    for i in 1..x:
+        yield i
+
+for n in countTo(3):
+    echo n
+
+proc countTo(x: int): iterator: int =
+    return iterator :int =
+        for i in 1..x:
+            yield i
+
+let counter  =  countTo(20)
+
+# able to preserve the sate of counter
+# not able to do with inline iterators
+# preserve the state of the iterator
+
+for n in counter():
+    echo n
+    if n == 5:
+        break
+
+for n in counter():
+    if n mod 2 == 0:
+        echo n
+
+# procedure that returns o closure iterator 
+proc repeat[T](x:T): iterator :T =
+    return iterator: T = 
+        while true:
+            yield x
+
+# nromal closure, pass it around and we can presve the data sotred iwth it
+# use a closure iterator as data 
+proc take[T](iter: iterator: T, n:int): iterator: T =
+    return iterator: T = 
+        var i = 0
+        for x in iter():
+            if i == n:
+                break
+            yield x
+            i += 1
+let threeHello = repeat("HelloWorld").take(3)
+    
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