From 2dc5e79a23ea630f88b1bef3faa43f52e2e807ef Mon Sep 17 00:00:00 2001
From: David Mak <chmakac@connect.ust.hk>
Date: Wed, 18 Dec 2024 16:44:57 +0800
Subject: [PATCH] [core] codegen/ndarray: Implement subscript assignment

Based on 5bed394e: core/ndstrides: implement subscript assignment

Overlapping is not handled. Currently it has undefined behavior.
---
 nac3core/src/codegen/stmt.rs       | 55 ++++++++++++++++++++++++++++--
 nac3standalone/demo/src/ndarray.py | 33 ++++++++++++++++++
 2 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/nac3core/src/codegen/stmt.rs b/nac3core/src/codegen/stmt.rs
index 3595528f..edebb4f0 100644
--- a/nac3core/src/codegen/stmt.rs
+++ b/nac3core/src/codegen/stmt.rs
@@ -16,7 +16,11 @@ use super::{
     gen_in_range_check,
     irrt::{handle_slice_indices, list_slice_assignment},
     macros::codegen_unreachable,
-    values::{ArrayLikeIndexer, ArraySliceValue, ListValue, RangeValue},
+    types::ndarray::NDArrayType,
+    values::{
+        ndarray::{RustNDIndex, ScalarOrNDArray},
+        ArrayLikeIndexer, ArraySliceValue, ListValue, ProxyValue, RangeValue,
+    },
     CodeGenContext, CodeGenerator,
 };
 use crate::{
@@ -411,7 +415,54 @@ pub fn gen_setitem<'ctx, G: CodeGenerator>(
             if *obj_id == ctx.primitives.ndarray.obj_id(&ctx.unifier).unwrap() =>
         {
             // Handle NDArray item assignment
-            todo!("ndarray subscript assignment is not yet implemented");
+            // Process target
+            let target = generator
+                .gen_expr(ctx, target)?
+                .unwrap()
+                .to_basic_value_enum(ctx, generator, target_ty)?;
+
+            // Process key
+            let key = RustNDIndex::from_subscript_expr(generator, ctx, key)?;
+
+            // Process value
+            let value = value.to_basic_value_enum(ctx, generator, value_ty)?;
+
+            // Reference code:
+            // ```python
+            // target = target[key]
+            // value = np.asarray(value)
+            //
+            // shape = np.broadcast_shape((target, value))
+            //
+            // target = np.broadcast_to(target, shape)
+            // value = np.broadcast_to(value, shape)
+            //
+            // # ...and finally copy 1-1 from value to target.
+            // ```
+
+            let target = NDArrayType::from_unifier_type(generator, ctx, target_ty)
+                .map_value(target.into_pointer_value(), None);
+            let target = target.index(generator, ctx, &key);
+
+            let value = ScalarOrNDArray::from_value(generator, ctx, (value_ty, value))
+                .to_ndarray(generator, ctx);
+
+            let broadcast_ndims = [target.get_type().ndims(), value.get_type().ndims()]
+                .iter()
+                .filter_map(|ndims| *ndims)
+                .max();
+            let broadcast_result = NDArrayType::new(
+                generator,
+                ctx.ctx,
+                value.get_type().element_type(),
+                broadcast_ndims,
+            )
+            .broadcast(generator, ctx, &[target, value]);
+
+            let target = broadcast_result.ndarrays[0];
+            let value = broadcast_result.ndarrays[1];
+
+            target.copy_data_from(generator, ctx, value);
         }
         _ => {
             panic!("encountered unknown target type: {}", ctx.unifier.stringify(target_ty));
diff --git a/nac3standalone/demo/src/ndarray.py b/nac3standalone/demo/src/ndarray.py
index 170ac14c..b668860f 100644
--- a/nac3standalone/demo/src/ndarray.py
+++ b/nac3standalone/demo/src/ndarray.py
@@ -276,6 +276,38 @@ def test_ndarray_broadcast_to():
     output_int32(np_shape(zs)[2])
     output_ndarray_float_3(zs)
 
+def test_ndarray_subscript_assignment():
+    xs = np_array([[11.0, 22.0, 33.0, 44.0], [55.0, 66.0, 77.0, 88.0]])
+
+    xs[0, 0] = 99.0
+    output_ndarray_float_2(xs)
+
+    xs[0] = 100.0
+    output_ndarray_float_2(xs)
+
+    xs[:, ::2] = 101.0
+    output_ndarray_float_2(xs)
+
+    xs[1:, 0] = 102.0
+    output_ndarray_float_2(xs)
+
+    xs[0] = np_array([-1.0, -2.0, -3.0, -4.0])
+    output_ndarray_float_2(xs)
+
+    xs[:] = np_array([-5.0, -6.0, -7.0, -8.0])
+    output_ndarray_float_2(xs)
+
+    # Test assignment with memory sharing
+    ys1 = np_reshape(xs, (2, 4))
+    ys2 = np_transpose(ys1)
+    ys3 = ys2[::-1, 0]
+    ys3[0] = -999.0
+
+    output_ndarray_float_2(xs)
+    output_ndarray_float_2(ys1)
+    output_ndarray_float_2(ys2)
+    output_ndarray_float_1(ys3)
+
 def test_ndarray_add():
     x = np_identity(2)
     y = x + np_ones([2, 2])
@@ -1653,6 +1685,7 @@ def run() -> int32:
     test_ndarray_transpose()
     test_ndarray_reshape()
     test_ndarray_broadcast_to()
+    test_ndarray_subscript_assignment()
 
     test_ndarray_add()
     test_ndarray_add_broadcast()