diff --git a/slige/compiler/check/checker.ts b/slige/compiler/check/checker.ts
index 7cbb76c..7d9572f 100644
--- a/slige/compiler/check/checker.ts
+++ b/slige/compiler/check/checker.ts
@@ -37,7 +37,7 @@ export class Checker {
             Ty({ tag: "null" });
     }
 
-    private checkLetStmtTy(stmt: ast.Stmt, kind: ast.LetStmt) {
+    private checkLetStmt(stmt: ast.Stmt, kind: ast.LetStmt) {
         if (this.stmtChecked.has(stmt.id)) {
             return;
         }
@@ -84,6 +84,42 @@ export class Checker {
         exhausted(k);
     }
 
+    public checkBreakStmt(stmt: ast.Stmt, kind: ast.BreakStmt) {
+        if (this.stmtChecked.has(stmt.id)) {
+            return;
+        }
+        this.stmtChecked.add(stmt.id);
+        const re = this.re.loopRes(stmt.id);
+        if (re.tag === "error") {
+            return;
+        }
+        if (re.tag !== "loop") {
+            if (kind.expr) {
+                this.report(
+                    `'${re.tag}'-style loop cannot break with value`,
+                    stmt.span,
+                );
+                return;
+            }
+            return;
+        }
+        const exTy = this.exprTys.get(re.expr.id)!;
+        if (!kind.expr) {
+            const ty = Ty({ tag: "null" });
+            const tyRes = this.resolveTys(ty, exTy);
+            if (!tyRes.ok) {
+                this.report(tyRes.val, stmt.span);
+                return;
+            }
+            this.exprTys.set(re.expr.id, tyRes.val)!;
+            return;
+        }
+        const ty = this.exprTy(kind.expr, exTy);
+        if (ty.kind.tag !== "error") {
+            this.exprTys.set(re.expr.id, ty);
+        }
+    }
+
     public checkAssignStmt(stmt: ast.Stmt, kind: ast.AssignStmt) {
         if (this.stmtChecked.has(stmt.id)) {
             return;
@@ -207,9 +243,9 @@ export class Checker {
         return Ty({ tag: "fn", item, kind, params, returnTy });
     }
 
-    public exprTy(expr: ast.Expr): Ty {
+    public exprTy(expr: ast.Expr, expected = Ty({ tag: "unknown" })): Ty {
         return this.exprTys.get(expr.id) ||
-            this.checkExpr(expr, Ty({ tag: "unknown" }));
+            this.checkExpr(expr, expected);
     }
 
     private checkExpr(expr: ast.Expr, expected: Ty): Ty {
@@ -256,13 +292,13 @@ export class Checker {
             case "if":
                 return this.checkIfExpr(expr, k, expected);
             case "loop":
-                return todo();
+                return this.checkLoopExpr(expr, k, expected);
             case "while":
-                return todo();
+                return this.checkWhileExpr(expr, k, expected);
             case "for":
                 return todo();
             case "c_for":
-                return todo();
+                return this.checkCForExpr(expr, k, expected);
         }
         exhausted(k);
     }
@@ -427,6 +463,80 @@ export class Checker {
         return bothRes.val;
     }
 
+    private checkLoopExpr(
+        expr: ast.Expr,
+        kind: ast.LoopExpr,
+        expected: Ty,
+    ): Ty {
+        this.exprTys.set(expr.id, expected);
+
+        const body = this.exprTy(kind.body, Ty({ tag: "unknown" }));
+        if (body.kind.tag !== "null") {
+            if (body.kind.tag !== "error") {
+                this.report("loop body must not yield a value", kind.body.span);
+            }
+            const ty = Ty({ tag: "error" });
+            this.exprTys.set(expr.id, ty);
+            return ty;
+        }
+
+        for (const { stmt, kind } of this.re.loopBreaks(expr.id)) {
+            this.checkBreakStmt(stmt, kind);
+        }
+
+        return this.exprTys.get(expr.id)!;
+    }
+
+    private checkWhileExpr(
+        expr: ast.Expr,
+        kind: ast.LoopExpr,
+        expected: Ty,
+    ): Ty {
+        const ty = Ty({ tag: "null" });
+        this.exprTys.set(expr.id, ty);
+
+        const body = this.exprTy(kind.body, Ty({ tag: "unknown" }));
+        if (body.kind.tag !== "null") {
+            if (body.kind.tag !== "error") {
+                this.report("loop body must not yield a value", kind.body.span);
+            }
+            const ty = Ty({ tag: "error" });
+            this.exprTys.set(expr.id, ty);
+            return ty;
+        }
+
+        for (const { stmt, kind } of this.re.loopBreaks(expr.id)) {
+            this.checkBreakStmt(stmt, kind);
+        }
+
+        return ty;
+    }
+
+    private checkCForExpr(
+        expr: ast.Expr,
+        kind: ast.LoopExpr,
+        expected: Ty,
+    ): Ty {
+        const ty = Ty({ tag: "null" });
+        this.exprTys.set(expr.id, ty);
+
+        const body = this.exprTy(kind.body, Ty({ tag: "unknown" }));
+        if (body.kind.tag !== "null") {
+            if (body.kind.tag !== "error") {
+                this.report("loop body must not yield a value", kind.body.span);
+            }
+            const ty = Ty({ tag: "error" });
+            this.exprTys.set(expr.id, ty);
+            return ty;
+        }
+
+        for (const { stmt, kind } of this.re.loopBreaks(expr.id)) {
+            this.checkBreakStmt(stmt, kind);
+        }
+
+        return ty;
+    }
+
     private tyTy(ty: ast.Ty): Ty {
         return this.tyTys.get(ty.id) ||
             this.checkTy(ty);
@@ -484,7 +594,7 @@ export class Checker {
                         return ty;
                     }
                     case "let": {
-                        this.checkLetStmtTy(patRes.kind.stmt, patRes.kind.kind);
+                        this.checkLetStmt(patRes.kind.stmt, patRes.kind.kind);
                         const ty = this.patTy(pat);
                         this.patTys.set(pat.id, ty);
                         return ty;
diff --git a/slige/compiler/middle/ast_lower.ts b/slige/compiler/middle/ast_lower.ts
index 0cb7612..4488aa7 100644
--- a/slige/compiler/middle/ast_lower.ts
+++ b/slige/compiler/middle/ast_lower.ts
@@ -50,6 +50,12 @@ export class FnLowerer {
 
     private paramLocals = new IdMap<LocalId, number>();
 
+    private loopInfos = new IdMap<AstId, {
+        loopBlock: BlockId;
+        endBlock: BlockId;
+        resultLocal?: LocalId;
+    }>();
+
     public constructor(
         private ctx: Ctx,
         private re: Resols,
@@ -107,7 +113,9 @@ export class FnLowerer {
             case "let":
                 return this.lowerLetStmt(stmt, k);
             case "return":
+                return todo(k.tag);
             case "break":
+                return this.lowerBreakStmt(stmt, k);
             case "continue":
                 return todo(k.tag);
             case "assign":
@@ -169,6 +177,27 @@ export class FnLowerer {
         exhausted(k);
     }
 
+    private lowerBreakStmt(stmt: ast.Stmt, kind: ast.BreakStmt) {
+        this.ch.checkBreakStmt(stmt, kind);
+        const re = this.re.loopRes(stmt.id);
+        if (re.tag === "error") {
+            return;
+        }
+        const info = this.loopInfos.get(re.expr.id)!;
+        if (kind.expr) {
+            const ty = this.ch.exprTy(kind.expr);
+            info.resultLocal = info.resultLocal ?? this.local(ty);
+            const rval = this.lowerExpr(kind.expr);
+            this.addStmt({
+                tag: "assign",
+                place: { local: info.resultLocal, proj: [] },
+                rval,
+            });
+        }
+        this.setTer({ tag: "goto", target: info.endBlock });
+        this.pushBlock();
+    }
+
     private lowerAssignStmt(stmt: ast.Stmt, kind: ast.AssignStmt) {
         this.ch.checkAssignStmt(stmt, kind);
         const rval = this.lowerExpr(kind.value);
@@ -262,10 +291,13 @@ export class FnLowerer {
             case "if":
                 return this.lowerIfExpr(expr, k);
             case "loop":
+                return this.lowerLoopExpr(expr, k);
             case "while":
+                return this.lowerWhileExpr(expr, k);
             case "for":
-            case "c_for":
                 return todo(k.tag);
+            case "c_for":
+                return this.lowerCForExpr(expr, k);
         }
         exhausted(k);
     }
@@ -367,8 +399,11 @@ export class FnLowerer {
             }
             const truthBlock = this.pushBlock();
             this.lowerExpr(kind.truthy);
-            const exit = this.pushBlock();
-            this.setTer({ tag: "goto", target: exit.id }, truthBlock);
+            const exit = this.createBlock();
+
+            this.setTer({ tag: "goto", target: exit.id });
+            this.pushCreatedBlock(exit);
+
             this.setTer({
                 tag: "switch",
                 discr,
@@ -382,6 +417,146 @@ export class FnLowerer {
         }
     }
 
+    private lowerLoopExpr(expr: ast.Expr, kind: ast.LoopExpr): RVal {
+        const entryBlock = this.currentBlock!;
+        const loopBlock = this.pushBlock();
+
+        const endBlock = this.createBlock();
+
+        const info = {
+            loopBlock: loopBlock.id,
+            endBlock: endBlock.id,
+            resultLocal: undefined,
+        };
+        this.loopInfos.set(expr.id, info);
+
+        const rval = this.lowerExpr(kind.body);
+        // ignore value;
+        void rval;
+
+        this.setTer({ tag: "goto", target: loopBlock.id });
+        this.setTer({ tag: "goto", target: loopBlock.id }, entryBlock);
+
+        this.pushCreatedBlock(endBlock);
+
+        if (info.resultLocal) {
+            const ty = this.ch.exprTy(expr);
+            return {
+                tag: "use",
+                operand: this.copyOrMoveLocal(info.resultLocal, ty),
+            };
+        } else {
+            return {
+                tag: "use",
+                operand: { tag: "const", val: { tag: "null" } },
+            };
+        }
+    }
+
+    private lowerWhileExpr(expr: ast.Expr, kind: ast.WhileExpr): RVal {
+        const enterBlock = this.currentBlock!;
+        const condBlock = this.pushBlock();
+        this.setTer({ tag: "goto", target: condBlock.id }, enterBlock);
+        const condTy = this.ch.exprTy(kind.cond);
+        const condLocal = this.localMut(condTy);
+        const condVal = this.lowerExpr(kind.cond);
+        this.addStmt({
+            tag: "assign",
+            place: { local: condLocal, proj: [] },
+            rval: condVal,
+        });
+
+        if (this.ch.exprTy(expr).kind.tag !== "null") {
+            throw new Error();
+        }
+        const bodyBlock = this.pushBlock();
+        const exitBlock = this.createBlock();
+
+        this.loopInfos.set(expr.id, {
+            loopBlock: condBlock.id,
+            endBlock: exitBlock.id,
+        });
+
+        this.lowerExpr(kind.body);
+        this.setTer({ tag: "goto", target: condBlock.id });
+
+        this.pushCreatedBlock(exitBlock);
+
+        this.setTer({
+            tag: "switch",
+            discr: this.copyOrMoveLocal(condLocal, condTy),
+            targets: [{ value: 1, target: bodyBlock.id }],
+            otherwise: exitBlock.id,
+        }, condBlock);
+        return {
+            tag: "use",
+            operand: { tag: "const", val: { tag: "null" } },
+        };
+    }
+
+    private lowerCForExpr(expr: ast.Expr, kind: ast.CForExpr): RVal {
+        kind.decl && this.lowerStmt(kind.decl);
+        const enterBlock = this.currentBlock!;
+
+        if (this.ch.exprTy(expr).kind.tag !== "null") {
+            throw new Error();
+        }
+
+        let loopBlock: Block;
+        const exitBlock = this.createBlock();
+
+        if (kind.cond) {
+            const condBlock = this.pushBlock();
+            this.setTer({ tag: "goto", target: condBlock.id }, enterBlock);
+            const condTy = this.ch.exprTy(kind.cond);
+            const condLocal = this.localMut(condTy);
+            const condVal = this.lowerExpr(kind.cond);
+            this.addStmt({
+                tag: "assign",
+                place: { local: condLocal, proj: [] },
+                rval: condVal,
+            });
+
+            const bodyBlock = this.pushBlock();
+
+            this.setTer({
+                tag: "switch",
+                discr: this.copyOrMoveLocal(condLocal, condTy),
+                targets: [{ value: 1, target: bodyBlock.id }],
+                otherwise: exitBlock.id,
+            }, condBlock);
+
+            loopBlock = condBlock;
+
+            this.loopInfos.set(expr.id, {
+                loopBlock: condBlock.id,
+                endBlock: exitBlock.id,
+            });
+        } else {
+            loopBlock = this.pushBlock();
+
+            this.setTer({ tag: "goto", target: loopBlock.id }, loopBlock);
+
+            this.loopInfos.set(expr.id, {
+                loopBlock: loopBlock.id,
+                endBlock: exitBlock.id,
+            });
+        }
+
+        this.lowerExpr(kind.body);
+        if (kind.incr) {
+            this.lowerStmt(kind.incr);
+        }
+
+        this.setTer({ tag: "goto", target: loopBlock.id });
+
+        this.pushCreatedBlock(exitBlock);
+        return {
+            tag: "use",
+            operand: { tag: "const", val: { tag: "null" } },
+        };
+    }
+
     private lowerExprToOperand(expr: ast.Expr): Operand {
         const k = expr.kind;
         switch (k.tag) {
@@ -510,6 +685,21 @@ export class FnLowerer {
         return block;
     }
 
+    private createBlock(): Block {
+        const id = this.blockIds.nextThenStep();
+        const block: Block = {
+            id,
+            stmts: [],
+            terminator: { kind: { tag: "unset" } },
+        };
+        return block;
+    }
+
+    private pushCreatedBlock(block: Block) {
+        this.blocks.set(block.id, block);
+        this.currentBlock = block;
+    }
+
     private setTer(kind: TerKind, block = this.currentBlock!) {
         block.terminator = { kind };
     }
diff --git a/slige/compiler/program.slg b/slige/compiler/program.slg
index 88879f2..7cbefd6 100644
--- a/slige/compiler/program.slg
+++ b/slige/compiler/program.slg
@@ -1,8 +1,6 @@
 
 fn main() {
-    let mut a = 5;
-
-    a = 10;
+    for (let mut i = 0; i < 10; i = i + 1) {}
 }
 
 
diff --git a/slige/compiler/resolve/cx.ts b/slige/compiler/resolve/cx.ts
index 3362d97..0abcbd2 100644
--- a/slige/compiler/resolve/cx.ts
+++ b/slige/compiler/resolve/cx.ts
@@ -33,6 +33,18 @@ export const ResolveError = (ident: ast.Ident): Resolve => ({
     kind: { tag: "error" },
 });
 
+export type LoopResolve =
+    | { tag: "error" }
+    | { tag: "loop"; expr: ast.Expr; kind: ast.LoopExpr }
+    | { tag: "while"; expr: ast.Expr; kind: ast.WhileExpr }
+    | { tag: "for"; expr: ast.Expr; kind: ast.ForExpr }
+    | { tag: "cfor"; expr: ast.Expr; kind: ast.CForExpr };
+
+export type LoopBreakResolve = {
+    stmt: ast.Stmt;
+    kind: ast.BreakStmt;
+};
+
 export type Redef = {
     ident: ast.Ident;
 };
diff --git a/slige/compiler/resolve/resolver.ts b/slige/compiler/resolve/resolver.ts
index 72626ca..0089566 100644
--- a/slige/compiler/resolve/resolver.ts
+++ b/slige/compiler/resolve/resolver.ts
@@ -13,6 +13,8 @@ import {
 import {
     FnSyms,
     LocalSyms,
+    LoopBreakResolve,
+    LoopResolve,
     PatResolve,
     PatResolveKind,
     Redef,
@@ -26,6 +28,8 @@ export class Resols {
     public constructor(
         private exprResols: IdMap<AstId, Resolve>,
         private patResols: IdMap<AstId, PatResolve>,
+        private loopsResols: IdMap<AstId, LoopResolve>,
+        private loopBreakResols: IdMap<AstId, LoopBreakResolve[]>,
     ) {}
 
     public exprRes(id: AstId): Resolve {
@@ -41,6 +45,20 @@ export class Resols {
         }
         return this.patResols.get(id)!;
     }
+
+    public loopRes(id: AstId): LoopResolve {
+        if (!this.loopsResols.has(id)) {
+            throw new Error();
+        }
+        return this.loopsResols.get(id)!;
+    }
+
+    public loopBreaks(id: AstId): LoopBreakResolve[] {
+        if (!this.loopBreakResols.has(id)) {
+            throw new Error();
+        }
+        return this.loopBreakResols.get(id)!;
+    }
 }
 
 export class Resolver implements ast.Visitor {
@@ -49,10 +67,14 @@ export class Resolver implements ast.Visitor {
     private syms: Syms = this.rootSyms;
 
     private exprResols = new IdMap<AstId, Resolve>();
-    private patResols = new IdMap<AstId, PatResolve>();
 
+    private patResols = new IdMap<AstId, PatResolve>();
     private patResolveStack: PatResolveKind[] = [];
 
+    private loopsResols = new IdMap<AstId, LoopResolve>();
+    private loopBreakResols = new IdMap<AstId, LoopBreakResolve[]>();
+    private loopResolveStack: LoopResolve[] = [{ tag: "error" }];
+
     public constructor(
         private ctx: Ctx,
         private entryFileAst: ast.File,
@@ -63,6 +85,8 @@ export class Resolver implements ast.Visitor {
         return new Resols(
             this.exprResols,
             this.patResols,
+            this.loopsResols,
+            this.loopBreakResols,
         );
     }
 
@@ -101,6 +125,25 @@ export class Resolver implements ast.Visitor {
         todo();
     }
 
+    visitBreakStmt(stmt: ast.Stmt, kind: ast.BreakStmt): ast.VisitRes {
+        const res = this.loopResolveStack.at(-1)!;
+        if (res.tag === "error") {
+            this.report("no loop to break", stmt.span);
+            return;
+        }
+        this.loopsResols.set(stmt.id, res);
+        this.loopBreakResols.get(res.expr.id)!.push({ stmt, kind });
+    }
+
+    visitContinueStmt(stmt: ast.Stmt): ast.VisitRes {
+        const res = this.loopResolveStack.at(-1)!;
+        if (res.tag === "error") {
+            this.report("no loop to continue", stmt.span);
+            return;
+        }
+        this.loopsResols.set(stmt.id, res);
+    }
+
     visitEnumItem(item: ast.Item, kind: ast.EnumItem): ast.VisitRes {
         todo();
     }
@@ -176,6 +219,42 @@ export class Resolver implements ast.Visitor {
         todo();
     }
 
+    visitLoopExpr(expr: ast.Expr, kind: ast.LoopExpr): ast.VisitRes {
+        this.genericVisitLoop(expr, kind.body, { tag: "loop", expr, kind });
+        return "stop";
+    }
+
+    visitWhileExpr(expr: ast.Expr, kind: ast.WhileExpr): ast.VisitRes {
+        ast.visitExpr(this, kind.cond);
+        this.genericVisitLoop(expr, kind.body, { tag: "while", expr, kind });
+        return "stop";
+    }
+
+    visitForExpr(expr: ast.Expr, kind: ast.ForExpr): ast.VisitRes {
+        todo();
+        return "stop";
+    }
+
+    visitCForExpr(expr: ast.Expr, kind: ast.CForExpr): ast.VisitRes {
+        const outerSyms = this.syms;
+        this.syms = new LocalSyms(this.syms);
+
+        kind.decl && ast.visitStmt(this, kind.decl);
+        kind.cond && ast.visitExpr(this, kind.cond);
+        kind.incr && ast.visitStmt(this, kind.incr);
+        this.genericVisitLoop(expr, kind.body, { tag: "cfor", expr, kind });
+        this.syms = outerSyms;
+        return "stop";
+    }
+
+    private genericVisitLoop(expr: ast.Expr, body: ast.Expr, res: LoopResolve) {
+        this.loopResolveStack.push(res);
+        this.loopBreakResols.set(expr.id, []);
+        ast.visitExpr(this, body);
+        this.loopResolveStack.pop();
+        return "stop";
+    }
+
     visitBindPat(pat: ast.Pat, kind: ast.BindPat): ast.VisitRes {
         this.patResols.set(pat.id, { pat, kind: this.patResolveStack.at(-1)! });
         const res = this.syms.defVal(kind.ident, {
diff --git a/slige/compiler/stringify/hir.ts b/slige/compiler/stringify/hir.ts
index b6599a8..cd2289e 100644
--- a/slige/compiler/stringify/hir.ts
+++ b/slige/compiler/stringify/hir.ts
@@ -22,10 +22,11 @@ export class HirStringifyer {
                 return "<error>;";
             case "item":
                 return this.item(k.item);
-            case "let":
+            case "let": {
                 return `let ${this.pat(k.pat)}${
                     k.expr && ` = ${this.expr(k.expr, d)}` || ""
                 };`;
+            }
             case "return":
                 return `return${k.expr && ` ${this.expr(k.expr, d)}` || ""};`;
             case "break":
@@ -33,7 +34,9 @@ export class HirStringifyer {
             case "continue":
                 return `continue;`;
             case "assign":
-                return `${this.expr(k.subject, d)} = ${this.expr(k.value, d)};`;
+                return `${this.expr(k.subject, d)} ${k.assignType} ${
+                    this.expr(k.value, d)
+                };`;
             case "expr":
                 return `${this.expr(k.expr, d)};`;
         }
@@ -119,10 +122,17 @@ export class HirStringifyer {
                     k.falsy && ` else ${this.expr(k.falsy, d)}` || ""
                 }`;
             case "loop":
+                return `loop ${this.expr(k.body, d)}`;
             case "while":
+                return `while ${this.expr(k.cond, d)} ${this.expr(k.body, d)}`;
             case "for":
-            case "c_for":
                 return todo(k.tag);
+            case "c_for":
+                return `for (${k.decl && this.stmt(k.decl, d) || ";"}${
+                    k.cond && ` ${this.expr(k.cond, d)}` || ""
+                };${k.incr && ` ${this.stmt(k.incr, d)}` || ""}) ${
+                    this.expr(k.body, d)
+                }`;
         }
         exhausted(k);
     }
diff --git a/slige/compiler/stringify/mir.ts b/slige/compiler/stringify/mir.ts
index 48b7708..e5aa5a9 100644
--- a/slige/compiler/stringify/mir.ts
+++ b/slige/compiler/stringify/mir.ts
@@ -52,11 +52,13 @@ export class MirFnStringifyer {
             .filter((local) => !fn.paramLocals.has(local.id))
             .map((local) => `#let ${this.localDef(local)}`)
             .join("\n");
-        return `fn ${fn.label}(${paramsStr}) {\n${localsStr}\n${
-            fn.blocks.values().toArray()
-                .map((block) => this.block(block))
-                .join("\n")
-        }\n}`.replaceAll("#", "    ");
+        const blocks = fn.blocks
+            .values()
+            .toArray()
+            .map((block) => this.block(block))
+            .join("\n");
+        return `fn ${fn.label}(${paramsStr}) {\n${localsStr}\n${blocks}\n}`
+            .replaceAll("#", "    ");
     }
 
     private localDef(local: Local): string {