From 6287ccff3b75a55cff121cd256e322a66ba1c449 Mon Sep 17 00:00:00 2001
From: Nao Pross <np@0hm.ch>
Date: Tue, 5 Mar 2024 00:45:05 +0100
Subject: Implement more shape checks

---
 mdpoly/algebra.py | 28 ++++++++++++++++++++++++----
 mdpoly/types.py   | 21 ++++++++++++++++++++-
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/mdpoly/algebra.py b/mdpoly/algebra.py
index 7085b42..670b537 100644
--- a/mdpoly/algebra.py
+++ b/mdpoly/algebra.py
@@ -161,7 +161,8 @@ class Add(Expr, HasRepr):
     def shape(self) -> Shape:
         """ See :py:meth:`mdpoly.abc.Expr.shape`. """
         if self.left.shape != self.right.shape:
-            raise InvalidShape(f"Cannot add shapes {self.left.shape} and {self.right.shape}.")
+            raise InvalidShape(f"Cannot add {self.left} and {self.right} with "
+                                f"shapes {self.left.shape} and {self.right.shape}.")
         return self.left.shape
 
     def to_repr(self, repr_type: type, state: State) -> tuple[Repr, State]:
@@ -494,9 +495,23 @@ class MatScalarMul(ReducibleExpr, MatrixAlgebra):
 
         raise InvalidShape(f"Either {self.left} or {self.right} must be a scalar.")
 
+
 @binary_operator(MatrixAlgebra, MatrixAlgebra)
-class MatInnerProd(Expr, MatrixAlgebra):
-    """ Inner product. """
+class MatDotProd(Expr, MatrixAlgebra):
+    """ Dot product. """
+
+    @property
+    def shape(self) -> Shape:
+        if not self.left.shape.is_row():
+            raise AlgebraicError(f"Left operand {self.left} must be a row!")
+
+        if not self.right.shape.is_col():
+            raise AlgebraicError(f"Right operand {self.right} must be a column!")
+
+        if self.left.shape.cols != self.right.shape.rows:
+            raise AlgebraicError(f"Rows of {self.right} and columns {self.left} do not match!")
+
+        return Shape.scalar()
 
 
 @binary_operator(MatrixAlgebra, MatrixAlgebra)
@@ -506,7 +521,12 @@ class MatMul(Expr, MatrixAlgebra):
     @property
     def shape(self) -> Shape:
         """ See :py:meth:`mdpoly.abc.Expr.shape`. """
-        raise NotImplementedError
+        if not self.left.shape.rows == self.right.shape.cols:
+            raise AlgebraicError("Cannot perform matrix multiplication between "
+                                 f"{self.left} and {self.right} (shapes {self.left.shape} and {self.right.shape})")
+
+        return Shape(self.left.shape.rows, self.right.shape.cols)
+
 
     def __repr__(self) -> str:
         return f"({self.left} @ {self.right})"
diff --git a/mdpoly/types.py b/mdpoly/types.py
index 46c5882..9e4ecb7 100644
--- a/mdpoly/types.py
+++ b/mdpoly/types.py
@@ -37,12 +37,31 @@ class Shape(NamedTuple):
             raise InvalidShape("Row vector must have dimension >= 1")
         return cls(1, n)
 
+    def is_row(self) -> bool:
+        return self.cols == 1
+
     @classmethod
-    def column(cls, n: int) -> Self:
+    def col(cls, n: int) -> Self:
         if n <= 0:
             raise InvalidShape("Column vector must have dimension >= 1")
         return cls(n, 1)
 
+    def is_col(self) -> bool:
+        return self.rows == 1
+
+    # --- aliases / shorthands ---
+
+    @property
+    def columns(self):
+        return self.cols
+
+    @classmethod
+    def column(cls, n: int) -> Self:
+        return cls.col(n)
+
+    def is_column(self) -> bool:
+        return self.is_col()
+
 
 class MatrixIndex(NamedTuple):
     """ Tuple to index an element of a matrix or vector. """
-- 
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