diff --git a/src/main/java/suite/funp/P0.java b/src/main/java/suite/funp/P0.java
index fe1317d03..f4c6cbf59 100644
--- a/src/main/java/suite/funp/P0.java
+++ b/src/main/java/suite/funp/P0.java
@@ -697,6 +697,7 @@ public enum Fct { // function capture type
 		MANUAL, // capture the variables and allocate a capture frame, to be uncaptured (freed) manually
 		NOSCOP, // no access to variables of outer scope
 		ONCE__, // capture the variables and allocate a capture frame, which is to be freed after first call; lambda cannot be called twice
+		SINGLE, // pass one variable
 		STACKF, // pass the stack frame, no need to capture; lambda lifetime equals to stack frame lifetime
 	}
 
diff --git a/src/main/java/suite/funp/P2.java b/src/main/java/suite/funp/P2.java
index 8f945473a..8cf762637 100644
--- a/src/main/java/suite/funp/P2.java
+++ b/src/main/java/suite/funp/P2.java
@@ -290,19 +290,43 @@ public <R> R apply(FixieFun5<Funp, Integer, Integer, Integer, Integer, R> fun) {
 		}
 	}
 
+	public static class FunpLambdaCapSingle implements Funp, P2.End {
+		public FunpVariable fpIn;
+		public FunpVariable frameVar;
+		public Funp frameValue;
+		public String vn;
+		public Funp expr;
+		public Fct fct;
+
+		public static FunpLambdaCapSingle of(FunpVariable fpIn, FunpVariable frameVar, Funp frameValue, String vn, Funp expr, Fct fct) {
+			var f = new FunpLambdaCapSingle();
+			f.fpIn = fpIn;
+			f.frameVar = frameVar;
+			f.frameValue = frameValue;
+			f.vn = vn;
+			f.expr = expr;
+			f.fct = fct;
+			return f;
+		}
+
+		public <R> R apply(FixieFun6<FunpVariable, FunpVariable, Funp, String, Funp, Fct, R> fun) {
+			return fun.apply(fpIn, frameVar, frameValue, vn, expr, fct);
+		}
+	}
+
 	public static class FunpLambdaCapture implements Funp, P2.End {
 		public FunpVariable fpIn;
 		public FunpVariable frameVar;
-		public Funp struct;
+		public Funp frameValue;
 		public String vn;
 		public Funp expr;
 		public Fct fct;
 
-		public static FunpLambdaCapture of(FunpVariable fpIn, FunpVariable frameVar, Funp struct, String vn, Funp expr, Fct fct) {
+		public static FunpLambdaCapture of(FunpVariable fpIn, FunpVariable frameVar, Funp frameValue, String vn, Funp expr, Fct fct) {
 			var f = new FunpLambdaCapture();
 			f.fpIn = fpIn;
 			f.frameVar = frameVar;
-			f.struct = struct;
+			f.frameValue = frameValue;
 			f.vn = vn;
 			f.expr = expr;
 			f.fct = fct;
@@ -310,7 +334,7 @@ public static FunpLambdaCapture of(FunpVariable fpIn, FunpVariable frameVar, Fun
 		}
 
 		public <R> R apply(FixieFun6<FunpVariable, FunpVariable, Funp, String, Funp, Fct, R> fun) {
-			return fun.apply(fpIn, frameVar, struct, vn, expr, fct);
+			return fun.apply(fpIn, frameVar, frameValue, vn, expr, fct);
 		}
 	}
 
diff --git a/src/main/java/suite/funp/p2/P21CaptureLambda.java b/src/main/java/suite/funp/p2/P21CaptureLambda.java
index 038ae9638..5632989cb 100644
--- a/src/main/java/suite/funp/p2/P21CaptureLambda.java
+++ b/src/main/java/suite/funp/p2/P21CaptureLambda.java
@@ -27,6 +27,8 @@
 import suite.funp.P0.FunpReference;
 import suite.funp.P0.FunpStruct;
 import suite.funp.P0.FunpVariable;
+import suite.funp.P2;
+import suite.funp.P2.FunpLambdaCapSingle;
 import suite.funp.P2.FunpLambdaCapture;
 import suite.funp.P2.FunpTypeAssign;
 import suite.inspect.Inspect;
@@ -120,6 +122,12 @@ else if (lambda.fct == Fct.MANUAL || lambda.fct == Fct.ONCE__) { // access from
 						if (li.captureSet.add(vn))
 							li.captures.add(Pair.of(vn, access(lambdaByFunp.get(lambda))));
 						return FunpField.of(FunpReference.of(li.cap), vn);
+					}
+					else if (lambda.fct == Fct.SINGLE) { // access from frame variable
+						var li = infoByLambda.get(lambda);
+						if (li.captureSet.add(vn))
+							li.captures.add(Pair.of(vn, access(lambdaByFunp.get(lambda))));
+						return li.cap;
 					} else if (lambda.fct == Fct.STACKF) // accessible through stack frame
 						return access(lambdaByFunp.get(lambda));
 					else
@@ -178,6 +186,11 @@ private Funp c_(Funp n) {
 							yield Funp_.fail(f, "scopeless lambda <" + vn + "> capturing variables " + li.captureSet);
 					}
 					case ONCE__ -> capturef.apply(false);
+					case SINGLE -> {
+						var capture = Read.from(captures).uniqueResult();
+						var pcap = FunpVariable.of(capture.k);
+						yield FunpLambdaCapSingle.of(pcap, li.cap, capture.v, vn, c(expr), fct);
+					}
 					case STACKF -> null;
 					default -> fail();
 					};
diff --git a/src/main/java/suite/funp/p2/P22InferType.java b/src/main/java/suite/funp/p2/P22InferType.java
index dfde9dcab..109f50490 100644
--- a/src/main/java/suite/funp/p2/P22InferType.java
+++ b/src/main/java/suite/funp/p2/P22InferType.java
@@ -333,9 +333,9 @@ else if (coerce == Coerce.POINTER)
 							.fold(PerMap.empty(), (e, p) -> e.put(p.k, p.v));
 				var env2 = env1.replace(vn, Pair.of(Fdt.L_MONO, tv));
 				return typeLambdaOf(tv, new Infer(env2, checks0, checks1, me).infer(expr));
-			})).applyIf(FunpLambdaCapture.class, f -> f.apply((fpIn, frameVar, frame, vn, expr, fct) -> {
+			})).applyIf(FunpLambdaCapture.class, f -> f.apply((fpIn, frameVar, frameValue, vn, expr, fct) -> {
 				var tv = new Reference();
-				var tf = infer(frame);
+				var tf = infer(frameValue);
 				var tr = typeRefOf(tf);
 				unify(f, tr, infer(fpIn));
 				var env1 = PerMap //
@@ -674,8 +674,8 @@ else if (Fdt.isSubs(fdt)) {
 				var expr2 = isPassByReg ? FunpAllocReg.of(lt.is, FunpDontCare.of(), expr1, opArg) : expr1;
 				var expr3 = f.name != null ? FunpRemark.of(f.name, expr2) : expr2;
 				return eraseRoutine(lt, frame, expr3);
-			})).applyIf(FunpLambdaCapture.class, f -> f.apply((fp0, frameVar, frame, vn, expr, fct) -> {
-				var size = getTypeSize(typeOf(frame));
+			})).applyIf(FunpLambdaCapture.class, f -> f.apply((fp0, frameVar, frameValue, vn, expr, fct) -> {
+				var size = getTypeSize(typeOf(frameValue));
 				var b = ps + ps; // return address and EBP
 				var lt = new LambdaType(f);
 				var isPassByReg = lt.isPassByReg;
@@ -698,6 +698,8 @@ else if (fct == Fct.ONCE__)
 					// the capture would free itself upon first call, therefore should not be called
 					// for the second time
 					expr3 = FunpHeapDealloc.of(false, size, FunpMemory.of(FunpFramePointer.of(), 0, ps), expr2);
+				else if (fct == Fct.SINGLE)
+					expr3 = expr2;
 				else
 					return fail();
 
diff --git a/src/main/resources/suite/funp/iter.fp b/src/main/resources/suite/funp/iter.fp
index 866a2b7a9..b30932086 100644
--- a/src/main/resources/suite/funp/iter.fp
+++ b/src/main/resources/suite/funp/iter.fp
@@ -50,7 +50,8 @@ define-global list-iter! list := do
 	type list = type-list ~
 	let { elems ~ size ~ } := list ~
 	let i := new! 0 ~
-	let has-next := () => capture (i* < size) ~
+	let cap := new! { elems, i, size, } ~
+	let has.next := () => capture (i* < size) ~
 	let next! := () => capture do
 		let i_ := i* ~
 		assign! i* := i_ + 1 ~
@@ -60,6 +61,7 @@ define-global list-iter! list := do
 		free! := () => capture1 do
 			uncapture has-next ~
 			uncapture next! ~
+			delete! cap ~
 			delete! i ~
 			()
 		~