3 files changed, 47 insertions, 14 deletions
diff --git a/examples/guess-number.ts b/examples/guess-number.ts
index aca3915..8f5d535 100644
--- a/examples/guess-number.ts
+++ b/examples/guess-number.ts
@@ -1,15 +1,33 @@
-import { Print, PutString, Bind, Kind1, JsExpr, ReadLine, Seq } from '../src/stdlib'
+import { Print, PutString, Bind, Kind1, JsExpr, ReadLine, Then, PutStringLn } from '../src/stdlib'
 
-export type main = Bind<
-  JsExpr<"Math.floor(Math.random() * 10)">,
-  StartGuessing
->
+export type main = [
+  PutStringLn<"You have 5 guesses">,
+  Bind<
+    JsExpr<"Math.floor(Math.random() * 10)">,
+    StartGuessing
+  >
+]
 
-interface AskForGuess<N extends number> extends Kind1<string> {
-  return: this['input'] extends `${N}` ? Print<"Yaya"> : Print<"naaah">
+interface AskForGuess<N extends number, Attempts extends 0[]> extends Kind1<string> {
+  return: `${this['input']}` extends `${N}`
+    ? PutStringLn<"Yay! You got it right!">
+    : Then<[
+      Print<`Wrong guess. Total attempts: ${
+        [...Attempts, 0] extends infer Ls extends 0[] ? Ls['length'] : 0
+      }`>,
+      (StartGuessing<[...Attempts, 0]> & { input: N })['return'],
+    ]>
 }
 
-interface StartGuessing extends Kind1<number> {
-  return: Bind<Seq<[PutString<"Your guess? ">, ReadLine]>, AskForGuess<this['input']>>
+interface StartGuessing<Attempts extends 0[] = []> extends Kind1<number> {
+  return: Attempts['length'] extends 5
+    ? PutStringLn<"Max attempts exceeded. Game over!">
+    : Bind<
+      Then<[
+        PutString<"Your guess? ">,
+        ReadLine
+      ]>,
+      AskForGuess<this['input'], Attempts>
+    >
 }
 
diff --git a/src/runtime.ts b/src/runtime.ts
index f2fc516..91393be 100644
--- a/src/runtime.ts
+++ b/src/runtime.ts
@@ -150,11 +150,7 @@ const evaluateType = async (effTyp: Type, node: Node): Promise<string[]> => {
 
     Seq: async () => {
       const [effectTyps] = effTyp.getTypeArguments()
-      const effectResults: string[] = []
-      for (const item of effectTyps?.getTupleElements() ?? []) {
-        effectResults.push(...(await evaluateType(item, node)))
-      }
-
+      const effectResults = await evalList(effectTyps?.getTupleElements() ?? [], node)
       const hash = uuid()
       addResult(hash, `[
         ${effectResults.map(r => `${RESULT_TYPE_NAME}[${JSON.stringify(r)}]`).join(', ')}
@@ -162,6 +158,15 @@ const evaluateType = async (effTyp: Type, node: Node): Promise<string[]> => {
       return [hash]
     },
 
+    Then: async () => {
+      const [effectTyps] = effTyp.getTypeArguments()
+      const effectResults = await evalList(effectTyps?.getTupleElements() ?? [], node)
+      const resultKey = effectResults[effectResults.length - 1]
+      const hash = uuid()
+      addResult(hash, `${RESULT_TYPE_NAME}[${JSON.stringify(resultKey)}]['output']`)
+      return [hash]
+    },
+
     _: async () => {
       if (name && customEffects[name]) {
         customEffects[name](...effTyp.getTypeArguments())
@@ -173,6 +178,14 @@ const evaluateType = async (effTyp: Type, node: Node): Promise<string[]> => {
   })
 }
 
+const evalList = async (effectTyps: Type[], node: Node) => {
+  const effectResults: string[] = []
+  for (const item of effectTyps ?? []) {
+    effectResults.push(...(await evaluateType(item, node)))
+  }
+  return effectResults
+}
+
 const main = async () => {
   if (typeRefNode) {
     const resultType = entryPoint?.getType()
diff --git a/src/stdlib/io.ts b/src/stdlib/io.ts
index d8e3ed2..d256628 100644
--- a/src/stdlib/io.ts
+++ b/src/stdlib/io.ts
@@ -9,5 +9,7 @@ export interface Bind<_Eff extends Effect, _Fn extends Kind1> extends Effect { }
 
 export interface Seq<_Effs extends Effect[]> extends Effect { }
 
+export interface Then<_Effs extends Effect[]> extends Effect { }
+
 export interface DefineEffect<_Name extends string, _Func extends string> extends Effect { }