From 16079a8a21d5d6a9277203fec8ed4b6ed4575f16 Mon Sep 17 00:00:00 2001
From: CAIMEOX <38813005+CAIMEOX@users.noreply.github.com>
Date: Fri, 3 Jan 2025 13:36:31 +0800
Subject: [PATCH] fix: counterexample function

---
 src/lib/feat/enumerate.mbt |  3 +--
 src/lib/gen_wbtest.mbt     | 17 +++++++++++++++++
 src/lib/testable.mbt       |  2 +-
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/lib/feat/enumerate.mbt b/src/lib/feat/enumerate.mbt
index 87b9dce..6e01d20 100644
--- a/src/lib/feat/enumerate.mbt
+++ b/src/lib/feat/enumerate.mbt
@@ -25,8 +25,7 @@ pub fn singleton[T](val : T) -> Enumerate[T] {
 
 ///|
 pub fn en_index[T](self : Enumerate[T], idx : BigInt) -> T {
-  let fin = self.parts
-  loop fin, idx {
+  loop self.parts, idx {
     Nil, _ => abort("index out of bounds")
     Cons(f, rest), i =>
       if i < f.fCard {
diff --git a/src/lib/gen_wbtest.mbt b/src/lib/gen_wbtest.mbt
index 21d0fe4..7604a3e 100644
--- a/src/lib/gen_wbtest.mbt
+++ b/src/lib/gen_wbtest.mbt
@@ -14,6 +14,16 @@ test "feat nat" {
   )
 }
 
+test "feat nat index" {
+  let x = [0N, 1, 2, 3, 4, 5, 6].map(fn(x) {
+    (@feat.Enumerable::enumerate() : @feat.Enumerate[Nat]).en_index(x)
+  })
+  inspect!(
+    x,
+    content="[Zero, Succ(Zero), Succ(Succ(Zero)), Succ(Succ(Succ(Zero))), Succ(Succ(Succ(Succ(Zero)))), Succ(Succ(Succ(Succ(Succ(Zero))))), Succ(Succ(Succ(Succ(Succ(Succ(Zero))))))]",
+  )
+}
+
 ///|
 enum SingleTree {
   Leaf(Bool)
@@ -76,6 +86,13 @@ test "feat tree" {
   )
 }
 
+test "index large" {
+  let eTree : @feat.Enumerate[SingleTree] = @feat.Enumerable::enumerate()
+  for i = 100000N; i > 0; i = i - 1 {
+    eTree.en_index(i) |> ignore
+  }
+}
+
 test "nat" {
   inspect!(
     nat().samples(size=50),
diff --git a/src/lib/testable.mbt b/src/lib/testable.mbt
index 9737f8e..c62246b 100644
--- a/src/lib/testable.mbt
+++ b/src/lib/testable.mbt
@@ -177,7 +177,7 @@ pub fn forall_shrink[T : Testable, A : Show](
   gen.bind(fn(x) {
     shrinking(shrinker, x, fn(a : A) {
       let s = a.to_string()
-      counterexample(f(x), s)
+      counterexample(f(a), s)
     })._
   })
 }