Add array slice method

Author: Folyd

aiscript-vm/src/builtins/array.rs

@@ -19,6 +19,8 @@ pub(crate) fn define_array_methods(ctx: Context) -> HashMap<InternedString, Buil
         // Ordering operations
         ("sort", BuiltinMethod(sort)),
         ("reverse", BuiltinMethod(reverse)),
+        // Subarray operations
+        ("slice", BuiltinMethod(slice)),
     ]
     .into_iter()
     .map(|(name, f)| (ctx.intern_static(name), f))
@@ -233,6 +235,51 @@ fn index<'gc>(
     )))
 }
 
+// Returns a shallow copy of a portion of the array
+fn slice<'gc>(
+    mc: &'gc Mutation<'gc>,
+    receiver: Value<'gc>,
+    args: Vec<Value<'gc>>,
+) -> Result<Value<'gc>, VmError> {
+    let list = receiver.as_array()?;
+
+    if args.is_empty() {
+        return Err(VmError::RuntimeError(
+            "slice: expected at least 1 argument".into(),
+        ));
+    }
+
+    let start = float_arg!(&args, 0, "slice")? as isize;
+
+    let list_ref = list.borrow();
+    let list_len = list_ref.data.len() as isize;
+
+    // Calculate start index (handle negative indices)
+    let start_idx = if start < 0 {
+        (list_len + start).max(0) as usize
+    } else {
+        start.min(list_len) as usize
+    };
+
+    // Calculate end index (handle negative indices and optional end parameter)
+    let end_idx = if args.len() > 1 {
+        let end = float_arg!(&args, 1, "slice")? as isize;
+        if end < 0 {
+            (list_len + end).max(0) as usize
+        } else {
+            end.min(list_len) as usize
+        }
+    } else {
+        list_len as usize
+    };
+
+    // Create a new array with the sliced elements
+    let start_idx = start_idx.min(end_idx); // Ensure start <= end
+    let result = list_ref.data[start_idx..end_idx].to_vec();
+
+    Ok(Value::array(mc, result))
+}
+
 // Return the number of times x appears in the list
 fn count<'gc>(
     _mc: &'gc Mutation<'gc>,

tests/integration/builtin_methods/array.ai

@@ -73,6 +73,19 @@ print(empty);  // expect: [1]
 numbers.clear();
 print(numbers);  // expect: []
 
+// Test slice method
+let nums = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+print(nums.slice(3, 7));      // expect: [3, 4, 5, 6]
+print(nums.slice(5));         // expect: [5, 6, 7, 8, 9]
+print(nums.slice(-3));        // expect: [7, 8, 9]
+print(nums.slice(-6, -2));    // expect: [4, 5, 6, 7]
+print(nums.slice(8, 5));      // expect: []
+
+// Complex examples
+let letters = ["a", "b", "c", "d", "e"];
+let reversed = letters.slice(1, 4).reverse();
+print(reversed);  // expect: [d, c, b]
+
 let nums = [1, 5, 2, 4, 3].sort();
 print(nums.pop(0));  // expect: 1
 print(nums);  // expect: [2, 3, 4, 5]