feat: add array enumerate

Author: olehmisar

README.md

@@ -128,6 +128,16 @@ use nodash::ArrayExtensions;
 assert([1, 2, 3].pad_end::<5>(0) == [1, 2, 3, 0, 0]);
 ```
 
+#### `enumerate`
+
+Returns an array of tuples, where each tuple contains the index and the value of the array element.
+
+```rs
+use nodash::ArrayExtensions;
+
+assert(["a", "b", "c"].enumerate() == [(0, "a"), (1, "b"), (2, "c")]);
+```
+
 ### `pack_bytes`
 
 Packs `[u8; N]` into `[Field; N / 31 + 1]`. Useful, if you need to get a hash over bytes. I.e., `pedersen_hash(pack_bytes(bytes))` will be MUCH cheaper than `pedersen_hash(bytes)`.

src/array.nr

@@ -37,6 +37,14 @@ impl<T, let N: u32> crate::ArrayExtensions<T, N> for [T; N] {
         }
         res
     }
+
+    fn enumerate(self) -> [(u32, T); N] {
+        let mut res = [(0, self[0]); N]; // TODO: should I use std::zeroed() instead?
+        for i in 1..N {
+            res[i] = (i as u32, self[i]);
+        }
+        res
+    }
 }
 
 // TODO: write tests
@@ -82,4 +90,9 @@ mod tests {
     fn test_pad_end() {
         assert([1, 2, 3].pad_end::<5>(0) == [1, 2, 3, 0, 0]);
     }
+
+    #[test]
+    fn test_enumerate() {
+        assert(["a", "b", "c"].enumerate() == [(0, "a"), (1, "b"), (2, "c")]);
+    }
 }

src/lib.nr

@@ -8,9 +8,10 @@ pub use array::pack_bytes;
 pub use math::{clamp, div_ceil, sqrt::sqrt};
 pub use string::{str_to_u64, to_hex_string_bytes};
 
-trait ArrayExtensions<T, let N: u32> {
+pub trait ArrayExtensions<T, let N: u32> {
     fn slice<let L: u32>(self, start: u32) -> [T; L];
     fn concat<let M: u32>(self, other: [T; M]) -> [T; N + M];
     fn pad_start<let M: u32>(self, pad_value: T) -> [T; M];
     fn pad_end<let M: u32>(self, pad_value: T) -> [T; M];
+    fn enumerate(self) -> [(u32, T); N];
 }