[FEATURE] Shape Manipulation Operations

PLAN.md

@@ -81,9 +81,9 @@ General formula: `flat = Σ(indices[d] * product(shape[d+1..]))`
 
 **Goal**: `reshape`, `transpose`, `flatten`. All return new arrays (copies).
 
-- [ ] **4.1** `reshape(self, allocator, new_shape) → NDArray` — validate `product(new_shape) == product(old_shape)`, create new NDArray, copy data (`@memcpy`), assign new shape
-- [ ] **4.2** `transpose(self, allocator) → NDArray` — 2D only. Create new `(cols, rows)` array, copy `result[j][i] = self[i][j]`
-- [ ] **4.3** `flatten(self, allocator) → NDArray` — reshape to `[total_elements]`
+- [X] **4.1** `reshape(self, allocator, new_shape) → NDArray` — validate `product(new_shape) == product(old_shape)`, create new NDArray, copy data (`@memcpy`), assign new shape
+- [X] **4.2** `transpose(self, allocator) → NDArray` — 2D only. Create new `(cols, rows)` array, copy `result[j][i] = self[i][j]`
+- [X] **4.3** `flatten(self, allocator) → NDArray` — reshape to `[total_elements]`
 - [ ] **4.4** `squeeze(self, allocator) → NDArray` — remove dimensions of size 1 from shape, copy data
 - [ ] **4.5** Tests: reshape `(2, 6)` → `(3, 4)`, verify values preserved. Transpose `(3, 4)` → verify `(4, 3)` with correct element positions
 

README.md

@@ -1,4 +1,4 @@
-# num-wasm
+# nw.js
 
 A NumPy-like array library written in Zig, compiled to WebAssembly for JavaScript/TypeScript.
 
@@ -68,17 +68,17 @@ These simplifications keep the codebase approachable. They can be upgraded later
 
 ## Roadmap
 
-| Phase | Feature | Status |
-|-------|---------|--------|
-| 1 | Toolchain setup, hello WASM | Done |
-| 2 | NDArray core data structure | Done |
-| 3 | Array creation functions | Done |
-| 4 | Shape manipulation (reshape, transpose, flatten) | Upcoming |
-| 5 | Broadcasting | Upcoming |
-| 6 | Element-wise operations (add, multiply, sqrt, etc.) | Upcoming |
-| 7 | Reduction operations (sum, mean, max, min) | Upcoming |
-| 8 | Slicing and indexing | Upcoming |
-| 9 | Linear algebra (dot, matmul) | Upcoming |
-| 10 | JS glue library (clean API) | Upcoming |
+| Phase | Feature                                             | Status   |
+| ----- | --------------------------------------------------- | -------- |
+| 1     | Toolchain setup, hello WASM                         | Done     |
+| 2     | NDArray core data structure                         | Done     |
+| 3     | Array creation functions                            | Done     |
+| 4     | Shape manipulation (reshape, transpose, flatten)    | Upcoming |
+| 5     | Broadcasting                                        | Upcoming |
+| 6     | Element-wise operations (add, multiply, sqrt, etc.) | Upcoming |
+| 7     | Reduction operations (sum, mean, max, min)          | Upcoming |
+| 8     | Slicing and indexing                                | Upcoming |
+| 9     | Linear algebra (dot, matmul)                        | Upcoming |
+| 10    | JS glue library (clean API)                         | Upcoming |
 
 See [PLAN.md](./PLAN.md) for detailed implementation plans.

src/core/shape.zig

@@ -0,0 +1,39 @@
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+const testing = std.testing;
+
+const NDArray = @import("ndarray.zig").NDArray;
+
+pub fn reshape(allocator: Allocator, arr: *const NDArray, new_shape: []const usize) !NDArray {
+    var new_total: usize = 1;
+    for (new_shape) |size| {
+        new_total *= size;
+    }
+
+    if (new_total != arr.data.len) return error.ShapeMismatch;
+
+    const res = try NDArray.init(allocator, new_shape);
+    @memcpy(res.data, arr.data);
+
+    return res;
+}
+
+pub fn transpose(allocator: Allocator, arr: *const NDArray) !NDArray {
+    if (arr.ndim != 2) return error.MismatchDimension;
+
+    const rows = arr.shape[0];
+    const cols = arr.shape[1];
+    const res = try NDArray.init(allocator, &[_]usize{ cols, rows });
+
+    for (0..cols) |c| {
+        for (0..rows) |r| {
+            res.setItem(&[_]usize{ c, r }, arr.getItem(&[_]usize{ r, c }));
+        }
+    }
+
+    return res;
+}
+
+pub fn flatten(allocator: Allocator, arr: *const NDArray) !NDArray {
+    return reshape(allocator, arr, &[_]usize{arr.data.len});
+}