Lazily consume the first N values

kgryte · kgryte · commit 125355471c80 · 2019-01-12T00:11:38.000-08:00
diff --git a/lib/node_modules/@stdlib/iter/slice/lib/main.js b/lib/node_modules/@stdlib/iter/slice/lib/main.js
@@ -91,24 +91,17 @@ function iterSlice( iterator, begin, end ) {
 		M = END;
 	}
 	n = M - N;
+	i = 0;
 
 	// Create an iterator protocol-compliant object:
 	iter = {};
 	setReadOnly( iter, 'next', next );
 	setReadOnly( iter, 'return', finish );
 
-	// If an environment supports `Symbol.iterator`, make the iterator iterable:
+	// If an environment supports `Symbol.iterator` and a provided iterator is iterable, make the iterator iterable:
 	if ( iteratorSymbol && isFunction( iterator[ iteratorSymbol ] ) ) {
 		setReadOnly( iter, iteratorSymbol, factory );
 	}
-
-	// Consume the first `N` values from the provided iterator...
-	if ( n > 0 ) {
-		for ( i = 0; i < N; i++ ) {
-			FLG = iterator.next().done;
-		}
-	}
-	i = 0;
 	return iter;
 
 	/**
@@ -120,8 +113,16 @@ function iterSlice( iterator, begin, end ) {
 	function next() {
 		var out;
 		var v;
+
 		i += 1;
-		if ( FLG || i > n ) {
+		if ( n > 0 && i < N ) {
+			// Lazily consume the first `N` values from the provided iterator...
+			for ( i = 0; i < N; i++ ) {
+				FLG = iterator.next().done;
+			}
+		}
+		n -= 1;
+		if ( FLG || n < 0 ) {
 			return {
 				'done': true
 			};
