From f64aaf5960287f776232f909e145ac3f72fec73c Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Sat, 13 Jul 2024 18:05:14 -0400
Subject: Add array:pairs()

---
 builtins/array.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

(limited to 'builtins/array.c')

diff --git a/builtins/array.c b/builtins/array.c
index 2d45591c..7086ff7f 100644
--- a/builtins/array.c
+++ b/builtins/array.c
@@ -320,6 +320,49 @@ public array_t Array$reversed(array_t array)
     return reversed;
 }
 
+typedef struct {
+    array_t arr;
+    int64_t i, j, item_size;
+    bool self_pairs:1, ordered:1;
+} pair_info_t;
+
+static bool next_pair(void *x, void *y, pair_info_t *info)
+{
+    if (info->i > info->arr.length || info->j > info->arr.length)
+        return false;
+
+    memcpy(x, info->arr.data + info->arr.stride * (info->i-1), info->item_size);
+    memcpy(y, info->arr.data + info->arr.stride * (info->j-1), info->item_size);
+    info->j += 1;
+    if (!info->self_pairs && info->j == info->i)
+        info->j += 1;
+
+    if (info->j > info->arr.length) {
+        info->i += 1;
+        if (info->ordered)
+            info->j = 1;
+        else if (info->self_pairs)
+            info->j = info->i;
+        else
+            info->j = info->i + 1;
+    }
+    return true;
+}
+
+public closure_t Array$pairs(array_t arr, bool self_pairs, bool ordered, const TypeInfo *type)
+{
+    return (closure_t){
+        .fn=next_pair,
+        .userdata=new(pair_info_t,
+            .arr=arr,
+            .i=1,
+            .j=self_pairs ? 1 : 2,
+            .item_size=get_item_size(type),
+            .self_pairs=self_pairs,
+            .ordered=ordered),
+    };
+}
+
 public array_t Array$concat(array_t x, array_t y, const TypeInfo *type)
 {
     int64_t item_size = get_item_size(type);
-- 
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