feat: adds then effect + fixes guess number example

2 files changed, 20 insertions, 5 deletions

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 { }