Add display of expressions to circuit drawers

qiskit/circuit/quantumcircuit.py

@@ -1673,6 +1673,7 @@ def draw(
         initial_state: bool = False,
         cregbundle: bool = None,
         wire_order: list = None,
+        expr_len: int = 30,
     ):
         """Draw the quantum circuit. Use the output parameter to choose the drawing format:
 
@@ -1766,6 +1767,9 @@ def draw(
             wire_order (list): Optional. A list of integers used to reorder the display
                 of the bits. The list must have an entry for every bit with the bits
                 in the range 0 to (``num_qubits`` + ``num_clbits``).
+            expr_len (int): Optional. The number of characters to display if an :class:`~.expr.Expr`
+                is used for the condition in a :class:`.ControlFlowOp`. If this number is exceeded,
+                the string will be truncated at that number and '...' added to the end.
 
         Returns:
             :class:`.TextDrawing` or :class:`matplotlib.figure` or :class:`PIL.Image` or
@@ -1818,6 +1822,7 @@ def draw(
             initial_state=initial_state,
             cregbundle=cregbundle,
             wire_order=wire_order,
+            expr_len=expr_len,
         )
 
     def size(

qiskit/visualization/circuit/_utils.py

@@ -428,7 +428,7 @@ def _get_layered_instructions(
         for node in dag.topological_op_nodes():
             nodes.append([node])
     else:
-        nodes = _LayerSpooler(dag, justify, measure_map, wire_map)
+        nodes = _LayerSpooler(dag, justify, measure_map)
 
     # Optionally remove all idle wires and instructions that are on them and
     # on them only.
@@ -454,7 +454,7 @@ def _sorted_nodes(dag_layer):
     return nodes
 
 
-def _get_gate_span(qubits, node, wire_map):
+def _get_gate_span(qubits, node):
     """Get the list of qubits drawing this gate would cover
     qiskit-terra #2802
     """
@@ -470,7 +470,7 @@ def _get_gate_span(qubits, node, wire_map):
 
     # Because of wrapping boxes for mpl control flow ops, this
     # type of op must be the only op in the layer
-    if wire_map is not None and isinstance(node.op, ControlFlowOp):
+    if isinstance(node.op, ControlFlowOp):
         span = qubits
     elif node.cargs or getattr(node.op, "condition", None):
         span = qubits[min_index : len(qubits)]
@@ -480,28 +480,27 @@ def _get_gate_span(qubits, node, wire_map):
     return span
 
 
-def _any_crossover(qubits, node, nodes, wire_map):
+def _any_crossover(qubits, node, nodes):
     """Return True .IFF. 'node' crosses over any 'nodes'."""
-    gate_span = _get_gate_span(qubits, node, wire_map)
+    gate_span = _get_gate_span(qubits, node)
     all_indices = []
     for check_node in nodes:
         if check_node != node:
-            all_indices += _get_gate_span(qubits, check_node, wire_map)
+            all_indices += _get_gate_span(qubits, check_node)
     return any(i in gate_span for i in all_indices)
 
 
 class _LayerSpooler(list):
     """Manipulate list of layer dicts for _get_layered_instructions."""
 
-    def __init__(self, dag, justification, measure_map, wire_map):
+    def __init__(self, dag, justification, measure_map):
         """Create spool"""
         super().__init__()
         self.dag = dag
         self.qubits = dag.qubits
         self.clbits = dag.clbits
         self.justification = justification
         self.measure_map = measure_map
-        self.wire_map = wire_map
         self.cregs = [self.dag.cregs[reg] for reg in self.dag.cregs]
 
         if self.justification == "left":
@@ -534,7 +533,7 @@ def is_found_in(self, node, nodes):
 
     def insertable(self, node, nodes):
         """True .IFF. we can add 'node' to layer 'nodes'"""
-        return not _any_crossover(self.qubits, node, nodes, self.wire_map)
+        return not _any_crossover(self.qubits, node, nodes)
 
     def slide_from_left(self, node, index):
         """Insert node into first layer where there is no conflict going l > r"""

qiskit/visualization/circuit/circuit_visualization.py

@@ -62,6 +62,7 @@ def circuit_drawer(
     initial_state=False,
     cregbundle=None,
     wire_order=None,
+    expr_len=30,
 ):
     """Draw the quantum circuit. Use the output parameter to choose the drawing format:
 
@@ -156,6 +157,9 @@ def circuit_drawer(
         wire_order (list): Optional. A list of integers used to reorder the display
             of the bits. The list must have an entry for every bit with the bits
             in the range 0 to (num_qubits + num_clbits).
+        expr_len (int): Optional. The number of characters to display if an :class:`~.expr.Expr`
+            is used for the condition in a :class:`.ControlFlowOp`. If this number is exceeded,
+            the string will be truncated at that number and '...' added to the end.
 
     Returns:
         :class:`TextDrawing` or :class:`matplotlib.figure` or :class:`PIL.Image` or
@@ -188,6 +192,7 @@ def circuit_drawer(
             circuit_drawer(qc, output='mpl', style={'backgroundcolor': '#EEEEEE'})
     """
     image = None
+    expr_len = max(expr_len, 0)
     config = user_config.get_config()
     # Get default from config file else use text
     default_output = "text"
@@ -257,6 +262,7 @@ def circuit_drawer(
             initial_state=initial_state,
             cregbundle=cregbundle,
             wire_order=complete_wire_order,
+            expr_len=expr_len,
         )
     elif output == "latex":
         image = _latex_circuit_drawer(
@@ -304,6 +310,7 @@ def circuit_drawer(
             initial_state=initial_state,
             cregbundle=cregbundle,
             wire_order=complete_wire_order,
+            expr_len=expr_len,
         )
     else:
         raise VisualizationError(
@@ -334,6 +341,7 @@ def _text_circuit_drawer(
     cregbundle=None,
     encoding=None,
     wire_order=None,
+    expr_len=30,
 ):
     """Draws a circuit using ascii art.
 
@@ -363,6 +371,9 @@ def _text_circuit_drawer(
         wire_order (list): Optional. A list of integers used to reorder the display
             of the bits. The list must have an entry for every bit with the bits
             in the range 0 to (num_qubits + num_clbits).
+        expr_len (int): Optional. The number of characters to display if an :class:`~.expr.Expr`
+            is used for the condition in a :class:`.ControlFlowOp`. If this number is exceeded,
+            the string will be truncated at that number and '...' added to the end.
 
     Returns:
         TextDrawing: An instance that, when printed, draws the circuit in ascii art.
@@ -387,6 +398,7 @@ def _text_circuit_drawer(
         cregbundle=cregbundle,
         encoding=encoding,
         with_layout=with_layout,
+        expr_len=expr_len,
     )
     text_drawing.plotbarriers = plot_barriers
     text_drawing.line_length = fold
@@ -612,6 +624,7 @@ def _matplotlib_circuit_drawer(
     initial_state=False,
     cregbundle=None,
     wire_order=None,
+    expr_len=30,
 ):
     """Draw a quantum circuit based on matplotlib.
     If `%matplotlib inline` is invoked in a Jupyter notebook, it visualizes a circuit inline.
@@ -643,6 +656,9 @@ def _matplotlib_circuit_drawer(
         wire_order (list): Optional. A list of integers used to reorder the display
             of the bits. The list must have an entry for every bit with the bits
             in the range 0 to (num_qubits + num_clbits).
+        expr_len (int): Optional. The number of characters to display if an :class:`~.expr.Expr`
+            is used for the condition in a :class:`.ControlFlowOp`. If this number is exceeded,
+            the string will be truncated at that number and '...' added to the end.
 
     Returns:
         matplotlib.figure: a matplotlib figure object for the circuit diagram
@@ -673,5 +689,6 @@ def _matplotlib_circuit_drawer(
         initial_state=initial_state,
         cregbundle=cregbundle,
         with_layout=with_layout,
+        expr_len=expr_len,
     )
     return qcd.draw(filename)