2 files changed, 72 insertions, 9 deletions
diff --git a/mdpoly/leaves.py b/mdpoly/leaves.py
index 4dd487d..4032ead 100644
--- a/mdpoly/leaves.py
+++ b/mdpoly/leaves.py
@@ -1,8 +1,13 @@
-from .abc import Leaf
-from .types import Number, Shape
+from .abc import Leaf, Repr
+from .types import Number, Shape, MatrixIndex, PolyVarIndex, PolyIndex
+from .state import State
+from .representations import HasRepr
 
+from typing import TypeVar
 from dataclasses import dataclass
 
+T = TypeVar("T", bound=Repr)
+
 
 @dataclass(frozen=True)
 class Nothing(Leaf):
@@ -14,22 +19,42 @@ class Nothing(Leaf):
 
 
 @dataclass(frozen=True)
-class Const(Leaf):
+class Const(Leaf, HasRepr):
     """
-    A constant
+    A scalar constant
     """
     value: Number
     name: str = ""
-    shape: Shape = Shape.scalar()
+    shape: Shape = Shape.scalar
+
+    def to_repr(self, repr_type: type[T], state: State) -> T:
+        r = repr_type()
+        r.set(MatrixIndex.scalar, PolyIndex.constant, self.value)
+        return r, state
+
+    def __repr__(self) -> str:
+        if self.name:
+            return self.name
+
+        return repr(self.value)
 
 
 @dataclass(frozen=True)
-class Var(Leaf):
+class Var(Leaf, HasRepr):
     """
     Polynomial variable
     """
     name: str
-    shape: Shape = Shape.scalar()
+    shape: Shape = Shape.scalar
+
+    def to_repr(self, repr_type: type[T], state: State) -> T:
+        r = repr_type()
+        idx = PolyVarIndex(varindex=state.index(self), power=1)
+        r.set(MatrixIndex.scalar, PolyIndex(idx), 1)
+        return r, state
+
+    def __repr__(self) -> str:
+        return self.name
 
 
 @dataclass(frozen=True)
@@ -38,4 +63,7 @@ class Param(Leaf):
     A parameter
     """
     name: str
-    shape: Shape = Shape.scalar()
+    shape: Shape = Shape.scalar
+
+    def __repr__(self) -> str:
+        return self.name
diff --git a/mdpoly/types.py b/mdpoly/types.py
index 29e7b83..a0ea671 100644
--- a/mdpoly/types.py
+++ b/mdpoly/types.py
@@ -1,6 +1,12 @@
+from __future__ import annotations
+
 from .errors import InvalidShape
 
-from typing import Self, NamedTuple, Iterable
+from typing import Self, NamedTuple, Iterable, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .state import State
+    from .leaves import Var
 
 Number = int | float
 
@@ -17,10 +23,12 @@ class Shape(NamedTuple):
     cols: int
 
     @classmethod
+    @property
     def infer(cls) -> Self:
         return cls(-1, -1)
 
     @classmethod
+    @property
     def scalar(cls) -> Self:
         return cls(1, 1)
     
@@ -49,6 +57,12 @@ class MatrixIndex(NamedTuple):
     def infer(cls, row=-1, col=-1) -> Self:
         return cls(row, col)
 
+    @classmethod
+    @property
+    def scalar(cls):
+        """ Shorthand for index of a scalar """
+        return cls(row=0, col=0)
+
 
 class PolyVarIndex(NamedTuple):
     """ 
@@ -59,6 +73,16 @@ class PolyVarIndex(NamedTuple):
     varindex: int
     power: Number
 
+    @classmethod
+    @property
+    def constant(cls):
+        """ Special index for constants, which have no variable """
+        return cls(varindex=-1, power=0)
+
+    @classmethod
+    def of_var(cls, variable: Var, state: State, power: Number =1) -> Self:
+        return cls(varindex=state.index(variable), power=power)
+
 
 class PolyIndex(tuple[PolyVarIndex]):
     """
@@ -78,3 +102,14 @@ class PolyIndex(tuple[PolyVarIndex]):
         The with the PolyIndex above we can retrieve the coefficient 5 in front
         of xy^2.
     """
+
+    def __repr__(self) -> str:
+        name = self.__class__.__qualname__
+        indices = ", ".join(map(repr, self))
+        return f"{name}({indices})"
+
+    @classmethod
+    @property
+    def constant(cls):
+        """ Index of the constant term """
+        return cls(PolyVarIndex.constant)