diff --git a/demo.hlcsl b/demo.hlcsl
index 21a9019..eb90264 100644
--- a/demo.hlcsl
+++ b/demo.hlcsl
@@ -1,5 +1,5 @@
 
-(def nand (a b vin) (r) (
+(def nand (a b) (r) (
     (let (a_and_b) (relay_default_off a b))
     (set r (relay_default_on a_and_b vin))
 ))
@@ -45,3 +45,4 @@
     (set carry_out e1)
 ))
 
+
diff --git a/src/front.ts b/src/front.ts
index f2748f0..ee3a9e5 100644
--- a/src/front.ts
+++ b/src/front.ts
@@ -26,7 +26,7 @@ export function tokenize(text: string): Tok[] {
         )[0]
         .map(({ tok, line }) => ({ ty: tok, text: tok, line }))
         .map((tok) => {
-            if (/^[a-zA-Z_][a-zA-Z_0-9]*$/.test(tok.text)) {
+            if (/^[a-zA-Z_0-9]+$/.test(tok.text)) {
                 tok.ty = "ident";
             }
             return tok;
@@ -263,6 +263,8 @@ class DefResolver {
     private syms = new Map<string, Sym>([
         ["relay_default_off", { tag: "Builtin" }],
         ["relay_default_on", { tag: "Builtin" }],
+        ["gnd", { tag: "Builtin" }],
+        ["vin", { tag: "Builtin" }],
     ]);
     public resols = new Map<Expr, Sym>();
 
diff --git a/src/main.ts b/src/main.ts
index 315dbfb..73b81e3 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,6 +1,31 @@
 import * as front from "./front.ts";
 import * as ast from "./ast.ts";
 
+class ColorPrinter {
+    private process: Deno.ChildProcess;
+    private writer: WritableStreamDefaultWriter<Uint8Array<ArrayBufferLike>>;
+
+    constructor(language: string, theme = "github-dark") {
+        this.process = new Deno.Command("pygmentize", {
+            args: ["-l", language, "-O", `style=${theme}`],
+            stdin: "piped",
+            stdout: "inherit",
+        })
+            .spawn();
+        this.writer = this.process.stdin.getWriter();
+    }
+
+    async print(text: string): Promise<void> {
+        await this.writer.ready;
+        await this.writer.write(new TextEncoder().encode(text));
+    }
+
+    async close(): Promise<void> {
+        await this.writer.close();
+        await this.process.output();
+    }
+}
+
 class Ins {
     constructor(
         public line: number,
@@ -9,26 +34,33 @@ class Ins {
 }
 
 type InsKind =
+    | { tag: "Gnd" | "Vin" }
     | { tag: "Input"; idx: number }
     | { tag: "Set"; idx: number; value: Ins }
-    | { tag: "RelayDefaultOff" | "RelayDefaultOn"; args: Ins[] }
+    | { tag: "RelayDefaultOff" | "RelayDefaultOn"; a: Ins; b: Ins }
     | { tag: "Call"; def: ast.Def; args: Ins[] }
     | { tag: "Elem"; value: Ins; idx: number };
 
 class InsCx {
     public insts: Ins[] = [];
 
+    makeGnd(line: number): Ins {
+        return this.make(line, { tag: "Gnd" });
+    }
+    makeVin(line: number): Ins {
+        return this.make(line, { tag: "Vin" });
+    }
     makeInput(line: number, idx: number): Ins {
         return this.make(line, { tag: "Input", idx });
     }
     makeSet(line: number, idx: number, value: Ins): Ins {
         return this.make(line, { tag: "Set", idx, value });
     }
-    makeRelayDefaultOff(line: number, args: Ins[]): Ins {
-        return this.make(line, { tag: "RelayDefaultOff", args });
+    makeRelayDefaultOff(line: number, a: Ins, b: Ins): Ins {
+        return this.make(line, { tag: "RelayDefaultOff", a, b });
     }
-    makeRelayDefaultOn(line: number, args: Ins[]): Ins {
-        return this.make(line, { tag: "RelayDefaultOn", args });
+    makeRelayDefaultOn(line: number, a: Ins, b: Ins): Ins {
+        return this.make(line, { tag: "RelayDefaultOn", a, b });
     }
     makeCall(line: number, def: ast.Def, args: Ins[]): Ins {
         return this.make(line, { tag: "Call", def, args });
@@ -42,9 +74,16 @@ class InsCx {
         this.insts.push(ins);
         return ins;
     }
+}
+
+class Component {
+    constructor(
+        public def: ast.Def,
+        public insts: Ins[],
+    ) {}
 
     pretty(): string {
-        let result = "";
+        let result = `${this.def.ident}:\n`;
         let regIds = 0;
         const insRegs = new Map<Ins, number>();
 
@@ -57,6 +96,12 @@ class InsCx {
 
         for (const ins of this.insts) {
             switch (ins.kind.tag) {
+                case "Gnd":
+                    result += `  ${r(ins)} = gnd\n`;
+                    break;
+                case "Vin":
+                    result += `  ${r(ins)} = vin\n`;
+                    break;
                 case "Input":
                     result += `  ${r(ins)} = input ${ins.kind.idx}\n`;
                     break;
@@ -65,24 +110,26 @@ class InsCx {
                     break;
                 case "RelayDefaultOff":
                     result += `  ${r(ins)} = relay_default_off ${
-                        r(ins.kind.args[0])
-                    } ${r(ins.kind.args[1])}\n`;
+                        r(ins.kind.a)
+                    }, ${r(ins.kind.b)}\n`;
                     break;
                 case "RelayDefaultOn":
                     result += `  ${r(ins)} = relay_default_on ${
-                        r(ins.kind.args[0])
-                    } ${r(ins.kind.args[1])}\n`;
+                        r(ins.kind.a)
+                    }, ${r(ins.kind.b)}\n`;
                     break;
                 case "Call":
-                    result += `  ${r(ins)} = call @${ins.kind.def.ident} ${
-                        r(ins.kind.args[0])
-                    } ${r(ins.kind.args[1])}\n`;
+                    result += `  ${r(ins)} = call @${ins.kind.def.ident}, ${
+                        ins.kind.args.map((a) => r(a)).join(", ")
+                    }\n`;
                     break;
                 case "Elem":
                     result += `  ${r(ins)} = elem ${
                         r(ins.kind.value)
-                    } ${ins.kind.idx}\n`;
+                    }, ${ins.kind.idx}\n`;
                     break;
+                default:
+                    ins.kind satisfies never;
             }
         }
         return result;
@@ -90,19 +137,19 @@ class InsCx {
 }
 
 class DefLowerer {
-    private symIns = new Map<front.Sym, Ins>();
+    private cx = new InsCx();
     private letIns = new Map<ast.Stmt, Ins[]>();
 
     constructor(
-        private cx: InsCx,
         private def: ast.Def,
         private resols: Map<ast.Expr, front.Sym>,
     ) {}
 
-    lower() {
+    lower(): Component {
         for (const stmt of this.def.stmts) {
             this.lowerStmt(stmt);
         }
+        return new Component(this.def, this.cx.insts);
     }
 
     lowerStmt(stmt: ast.Stmt) {
@@ -114,7 +161,7 @@ class DefLowerer {
                         this.cx.makeSet(
                             stmt.line,
                             re.idx,
-                            this.lowerExpr(stmt.kind.expr),
+                            this.lowerExprToVal(stmt.kind.expr),
                         );
                         break;
                     case "Builtin":
@@ -140,6 +187,17 @@ class DefLowerer {
         }
     }
 
+    lowerExprToVal(expr: ast.Expr): Ins {
+        if (expr.kind.tag === "Call") {
+            return this.cx.makeElem(
+                expr.line,
+                this.lowerExpr(expr),
+                0,
+            );
+        }
+        return this.lowerExpr(expr);
+    }
+
     lowerExpr(expr: ast.Expr): Ins {
         switch (expr.kind.tag) {
             case "Ident": {
@@ -150,7 +208,15 @@ class DefLowerer {
                     case "Node": {
                         return this.letIns.get(re.stmt)![re.idx];
                     }
-                    case "Builtin":
+                    case "Builtin": {
+                        switch (expr.kind.ident) {
+                            case "gnd":
+                                return this.cx.makeGnd(expr.line);
+                            case "vin":
+                                return this.cx.makeVin(expr.line);
+                        }
+                        break;
+                    }
                     case "Output":
                     case "Def":
                         throw new Error();
@@ -168,16 +234,14 @@ class DefLowerer {
                             case "relay_default_off":
                                 return this.cx.makeRelayDefaultOff(
                                     expr.line,
-                                    expr.kind.args.map((expr) =>
-                                        this.lowerExpr(expr)
-                                    ),
+                                    this.lowerExprToVal(expr.kind.args[0]),
+                                    this.lowerExprToVal(expr.kind.args[1]),
                                 );
                             case "relay_default_on":
                                 return this.cx.makeRelayDefaultOn(
                                     expr.line,
-                                    expr.kind.args.map((expr) =>
-                                        this.lowerExpr(expr)
-                                    ),
+                                    this.lowerExprToVal(expr.kind.args[0]),
+                                    this.lowerExprToVal(expr.kind.args[1]),
                                 );
                             default:
                                 throw new Error();
@@ -188,7 +252,9 @@ class DefLowerer {
                         return this.cx.makeCall(
                             expr.line,
                             re.def,
-                            expr.kind.args.map((expr) => this.lowerExpr(expr)),
+                            expr.kind.args.map((expr) =>
+                                this.lowerExprToVal(expr)
+                            ),
                         );
                         break;
                     }
@@ -206,15 +272,117 @@ class DefLowerer {
     }
 }
 
+class IrInterpreter {
+    constructor(
+        private components: Map<ast.Def, Component>,
+    ) {}
+
+    eval(com: Component, inputs: boolean[]): boolean[] {
+        if (inputs.length !== com.def.inputs.length) {
+            throw new Error(
+                `incorrect arguments to component '${com.def.ident}'. expected ${com.def.inputs.length}, got ${inputs.length}`,
+            );
+        }
+        const outputs = new Array(com.def.outputs.length).fill(false);
+        const tups = new Map<Ins, boolean[]>();
+        const vals = new Map<Ins, boolean>();
+        for (const ins of com.insts) {
+            switch (ins.kind.tag) {
+                case "Gnd":
+                    vals.set(ins, false);
+                    break;
+                case "Vin":
+                    vals.set(ins, true);
+                    break;
+                case "Input":
+                    vals.set(ins, inputs[ins.kind.idx]);
+                    break;
+                case "Set":
+                    outputs[ins.kind.idx] = vals.get(ins.kind.value);
+                    break;
+                case "RelayDefaultOff":
+                    tups.set(
+                        ins,
+                        [
+                            vals.get(ins.kind.a)! &&
+                            vals.get(ins.kind.b)!,
+                        ],
+                    );
+                    break;
+                case "RelayDefaultOn":
+                    tups.set(
+                        ins,
+                        [
+                            !vals.get(ins.kind.a)! &&
+                            vals.get(ins.kind.b)!,
+                        ],
+                    );
+                    break;
+                case "Call":
+                    tups.set(
+                        ins,
+                        this.eval(
+                            this.components.get(ins.kind.def)!,
+                            ins.kind.args.map((arg) => vals.get(arg)!),
+                        ),
+                    );
+                    break;
+                case "Elem":
+                    vals.set(
+                        ins,
+                        tups.get(ins.kind.value)![ins.kind.idx],
+                    );
+                    break;
+                default:
+                    ins.kind satisfies never;
+            }
+        }
+        return outputs;
+    }
+}
+
 const text = await Deno.readTextFile(Deno.args[0]);
 const toks = front.tokenize(text);
 const sexprs = front.parseSExprs(toks);
 const defs = front.parseAst(sexprs);
 const resols = front.resolve(defs);
 
+const printer = new ColorPrinter("llvm");
+
+const components = new Map<ast.Def, Component>();
 for (const def of defs) {
-    console.log(`${def.ident}:`);
-    const cx = new InsCx();
-    new DefLowerer(cx, def, resols.get(def)!).lower();
-    console.log(cx.pretty());
+    const component = new DefLowerer(def, resols.get(def)!).lower();
+    components.set(def, component);
+    await printer.print(component.pretty());
+}
+await printer.close();
+
+const interpreter = new IrInterpreter(components);
+
+while (true) {
+    const line = prompt(">");
+    if (!line) {
+        break;
+    }
+    const s = front.parseSExprs(front.tokenize("(" + line + ")"))[0];
+
+    const ident = s.exprs?.[0].ident;
+    const args = s.exprs
+        ?.slice(1)
+        ?.map((s) =>
+            s.ident && /^[01]$/.test(s.ident) ? s.ident === "1" : null
+        );
+
+    if (!ident || !args || args.some((a) => a === null)) {
+        console.error(`error: malformed expression`);
+        continue;
+    }
+
+    const com = components.values().find((v) => v.def.ident === ident);
+    if (!com) {
+        throw new Error(`no component '${ident}'`);
+    }
+    const output = interpreter.eval(com, args as boolean[]);
+    const result = output.map((v) => v ? "1" : "0").join(" ");
+    console.log(`= ${result}`);
 }