From cc198178cb6449471cba32d46fad596fa7137d15 Mon Sep 17 00:00:00 2001
From: Texas Toland <texastoland@gmail.com>
Date: Tue, 19 Mar 2024 21:40:58 -0500
Subject: [PATCH] Initial jq `recurse()` implementation

BFS for jq parity and imperative to avoid call stack limit.
---
 stdlib-candidate/std-rfc/mod.nu     |  1 +
 stdlib-candidate/std-rfc/recurse.nu | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 stdlib-candidate/std-rfc/recurse.nu

diff --git a/stdlib-candidate/std-rfc/mod.nu b/stdlib-candidate/std-rfc/mod.nu
index d2c7dc9ee..4ea82ad3a 100644
--- a/stdlib-candidate/std-rfc/mod.nu
+++ b/stdlib-candidate/std-rfc/mod.nu
@@ -4,3 +4,4 @@ export module str/
 # commands
 export use fs.nu *
 export use set-env.nu *
+export use recurse.nu *
diff --git a/stdlib-candidate/std-rfc/recurse.nu b/stdlib-candidate/std-rfc/recurse.nu
new file mode 100644
index 000000000..803a3384b
--- /dev/null
+++ b/stdlib-candidate/std-rfc/recurse.nu
@@ -0,0 +1,23 @@
+export def main [
+    --filter: closure
+]: any -> list<any> {
+    mut todo = [$in]
+    mut done = []
+    while ($todo | length) > 0 {
+        # pop
+        let value = $todo | last
+        $todo = ($todo | drop)
+        # save
+        if $filter == null or ($value | do $filter $value) {
+            $done ++= [$value]
+        }
+        # push
+        $todo ++= (match ($value | describe --detailed | get type) {
+            table => ($value | values | flatten)
+            record => ($value | values)
+            list => $value
+            _ => continue
+        } | reverse)
+    }
+    $done
+}