feat: Define Const inline by default, and add a parameter to change…

… the parent (#1404)

Instead of always defining constants/functions/aliases at the root of
the hugr,
defaults to the current container when using a dataflow builder, adds
parameters to override it.

hugr-py/src/hugr/dfg.py

@@ -42,25 +42,29 @@ def define_function(
         name: str,
         input_types: TypeRow,
         type_params: list[TypeParam] | None = None,
+        parent: ToNode | None = None,
     ) -> Function:
         """Start building a function definition in the graph.
 
         Args:
             name: The name of the function.
             input_types: The input types for the function.
             type_params: The type parameters for the function, if polymorphic.
+            parent: The parent node of the constant. Defaults to the root node.
 
         Returns:
             The new function builder.
         """
+        parent_node = parent or self.hugr.root
         parent_op = ops.FuncDefn(name, input_types, type_params or [])
-        return Function.new_nested(parent_op, self.hugr)
+        return Function.new_nested(parent_op, self.hugr, parent_node)
 
-    def add_const(self, value: val.Value) -> Node:
+    def add_const(self, value: val.Value, parent: ToNode | None = None) -> Node:
         """Add a static constant to the graph.
 
         Args:
             value: The constant value to add.
+            parent: The parent node of the constant. Defaults to the root node.
 
         Returns:
             The node holding the :class:`Const <hugr.ops.Const>` operation.
@@ -71,11 +75,13 @@ def add_const(self, value: val.Value) -> Node:
             >>> dfg.hugr[const_n].op
             Const(TRUE)
         """
-        return self.hugr.add_node(ops.Const(value), self.hugr.root)
+        parent_node = parent or self.hugr.root
+        return self.hugr.add_node(ops.Const(value), parent_node)
 
-    def add_alias_defn(self, name: str, ty: Type) -> Node:
+    def add_alias_defn(self, name: str, ty: Type, parent: ToNode | None = None) -> Node:
         """Add a type alias definition."""
-        return self.hugr.add_node(ops.AliasDefn(name, ty), self.hugr.root)
+        parent_node = parent or self.hugr.root
+        return self.hugr.add_node(ops.AliasDefn(name, ty), parent_node)
 
 
 DP = TypeVar("DP", bound=ops.DfParentOp)
@@ -482,13 +488,17 @@ def add_state_order(self, src: Node, dst: Node) -> None:
         # adds edge to the right of all existing edges
         self.hugr.add_link(src.out(-1), dst.inp(-1))
 
-    def load(self, const: ToNode | val.Value) -> Node:
+    def load(
+        self, const: ToNode | val.Value, const_parent: ToNode | None = None
+    ) -> Node:
         """Load a constant into the graph as a dataflow value.
 
         Args:
             const: The constant to load, either a Value that will be added as a
-            child Const node then loaded, or a node corresponding to an existing
-            Const.
+                child Const node then loaded, or a node corresponding to an
+                existing Const.
+            const_parent: If `const` is a Value, the parent node for the new
+                constant definition. Defaults to the current dataflow container.
 
         Returns:
             The node holding the :class:`LoadConst <hugr.ops.LoadConst>`
@@ -503,7 +513,8 @@ def load(self, const: ToNode | val.Value) -> Node:
             LoadConst(Bool)
         """
         if isinstance(const, val.Value):
-            const = self.add_const(const)
+            const_parent = const_parent or self.parent_node
+            const = self.add_const(const, parent=const_parent)
         const_op = self.hugr._get_typed_op(const, ops.Const)
         load_op = ops.LoadConst(const_op.val.type_())