implement join for string_builder

1 files changed, 8 insertions, 0 deletions

diff --git a/src/gleam/string_builder.gleam b/src/gleam/string_builder.gleam
index 616da74..4db332c 100644
--- a/src/gleam/string_builder.gleam
+++ b/src/gleam/string_builder.gleam
@@ -1,3 +1,5 @@
+import gleam/list
+
 /// `StringBuilder` is a type used for efficiently building strings.
 ///
 /// When we append one string to another the strings must be copied to a
@@ -161,6 +163,12 @@ if javascript {
     "../gleam_stdlib.mjs" "length"
 }
 
+pub fn join(builders: List(StringBuilder), with sep: String) -> StringBuilder {
+  builders
+  |> list.intersperse(from_string(sep))
+  |> concat
+}
+
 /// Converts a builder to a new builder where the contents have been
 /// lowercased.
 ///