String slice tco (#338)

3 files changed, 39 insertions, 7 deletions

diff --git a/src/gleam/string.gleam b/src/gleam/string.gleam
index 1645894..9c1bc9e 100644
--- a/src/gleam/string.gleam
+++ b/src/gleam/string.gleam
@@ -710,9 +710,14 @@ if javascript {
 /// ```
 ///
 pub fn to_graphemes(string: String) -> List(String) {
+  do_to_graphemes(string, [])
+  |> list.reverse
+}
+
+pub fn do_to_graphemes(string: String, acc: List(String)) -> List(String) {
   case pop_grapheme(string) {
-    Ok(#(grapheme, rest)) -> [grapheme, ..to_graphemes(rest)]
-    _ -> []
+    Ok(#(grapheme, rest)) -> do_to_graphemes(rest, [grapheme, ..acc])
+    _ -> acc
   }
 }
 
diff --git a/test/gleam/list_test.gleam b/test/gleam/list_test.gleam
index 1ea4f42..f9a7f44 100644
--- a/test/gleam/list_test.gleam
+++ b/test/gleam/list_test.gleam
@@ -3,6 +3,14 @@ import gleam/int
 import gleam/list
 import gleam/should
 
+if erlang {
+  const recursion_test_cycles = 999999
+}
+
+if javascript {
+  const recursion_test_cycles = 16999
+}
+
 pub fn length_test() {
   list.length([])
   |> should.equal(0)
@@ -49,7 +57,7 @@ pub fn contains_test() {
   list.contains([], 1)
   |> should.be_false
 
-  list.repeat(0, 16999)
+  list.repeat(0, recursion_test_cycles)
   |> list.contains(1)
   |> should.equal(False)
 }
@@ -309,11 +317,11 @@ pub fn all_test() {
   list.all([], fn(_) { False })
   |> should.equal(True)
 
-  list.repeat(False, 16999)
+  list.repeat(False, recursion_test_cycles)
   |> list.all(fn(item) { item })
   |> should.equal(False)
 
-  list.repeat(True, 16999)
+  list.repeat(True, recursion_test_cycles)
   |> list.all(fn(item) { item })
   |> should.equal(True)
 
@@ -340,11 +348,11 @@ pub fn any_test() {
   list.any([], fn(_) { False })
   |> should.equal(False)
 
-  list.repeat(True, 16999)
+  list.repeat(True, recursion_test_cycles)
   |> list.any(fn(item) { item })
   |> should.equal(True)
 
-  list.repeat(False, 16999)
+  list.repeat(False, recursion_test_cycles)
   |> list.any(fn(item) { item })
   |> should.equal(False)
 
diff --git a/test/gleam/string_test.gleam b/test/gleam/string_test.gleam
index 2e595b1..7155ea6 100644
--- a/test/gleam/string_test.gleam
+++ b/test/gleam/string_test.gleam
@@ -3,6 +3,14 @@ import gleam/order
 import gleam/should
 import gleam/string
 
+if erlang {
+  const recursion_test_cycles = 999999
+}
+
+if javascript {
+  const recursion_test_cycles = 16999
+}
+
 pub fn length_test() {
   string.length("ß↑e̊")
   |> should.equal(3)
@@ -53,6 +61,12 @@ pub fn reverse_test() {
   |> string.reverse
   |> string.reverse
   |> should.equal("👶🏿")
+
+  "abc"
+  |> string.repeat(recursion_test_cycles)
+  |> string.reverse
+  |> string.starts_with("cba")
+  |> should.be_true
 }
 
 pub fn split_test() {
@@ -233,6 +247,11 @@ pub fn slice_test() {
   "👶🏿"
   |> string.slice(at_index: 0, length: 3)
   |> should.equal("👶🏿")
+
+  "aaa"
+  |> string.repeat(recursion_test_cycles)
+  |> string.slice(at_index: recursion_test_cycles / 2, length: 3)
+  |> should.equal("aaa")
 }
 
 pub fn crop_test() {