[core] codegen: Implement NDArrayValue::atleast_nd

Based on 9cfa2622: core/ndstrides: add NDArrayObject::atleast_nd.

nac3core/src/codegen/values/ndarray/mod.rs

@@ -19,10 +19,12 @@ use crate::codegen::{
 pub use contiguous::*;
 pub use indexing::*;
 pub use nditer::*;
+pub use view::*;
 
 mod contiguous;
 mod indexing;
 mod nditer;
+mod view;
 
 /// Proxy type for accessing an `NDArray` value in LLVM.
 #[derive(Copy, Clone)]

nac3core/src/codegen/values/ndarray/view.rs

@@ -0,0 +1,36 @@
+use std::iter::{once, repeat_n};
+
+use itertools::Itertools;
+
+use crate::codegen::{
+    values::ndarray::{NDArrayValue, RustNDIndex},
+    CodeGenContext, CodeGenerator,
+};
+
+impl<'ctx> NDArrayValue<'ctx> {
+    /// Make sure the ndarray is at least `ndmin`-dimensional.
+    ///
+    /// If this ndarray's `ndims` is less than `ndmin`, a view is created on this with 1s prepended
+    /// to the shape. Otherwise, this function does nothing and return this ndarray.
+    #[must_use]
+    pub fn atleast_nd<G: CodeGenerator + ?Sized>(
+        &self,
+        generator: &mut G,
+        ctx: &mut CodeGenContext<'ctx, '_>,
+        ndmin: u64,
+    ) -> Self {
+        assert!(self.ndims.is_some(), "NDArrayValue::atleast_nd is only supported for instances with compile-time known ndims (self.ndims = Some(...))");
+
+        let ndims = self.ndims.unwrap();
+
+        if ndims < ndmin {
+            // Extend the dimensions with np.newaxis.
+            let indices = repeat_n(RustNDIndex::NewAxis, (ndmin - ndims) as usize)
+                .chain(once(RustNDIndex::Ellipsis))
+                .collect_vec();
+            self.index(generator, ctx, &indices)
+        } else {
+            *self
+        }
+    }
+}