[CQT-458] add add_instruction to the circuit builder

CHANGELOG.md

@@ -27,6 +27,7 @@ arbitrarily applied mapper pass.
 - `CircuitAnalyzer` analyzer pass for computing structural circuit metrics (size, interaction graph, gate dependency graph, density)
 - `Can2CZDecomposer` to decompose arbitrary two-qubit gates.
 - The following 2-qubit gates: `CV`, `CY`, `DCNOT`, `ECR`, `ISWAP`, `InvSqrtSWAP`, `M`, `MS`, `SqrtISWAP`, and `SqrtSWAP`
+- Add `add_instruction` method to the `CircuitBuilder`
 
 ## [ 0.9.0 ] - [ 2025-12-19 ]
 

opensquirrel/circuit_builder.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from collections import OrderedDict
+from collections.abc import Iterable
 from copy import deepcopy
 from functools import partial
 from typing import Any
@@ -190,6 +191,20 @@ def _expand_sgmq_args(self, attr: str, args: tuple[Any, ...]) -> list[tuple[Any,
         remaining_args = args[1:]
         return [(first, *remaining_args) for first in expanded_first]
 
+    def add_instruction(self, instruction: Instruction | Iterable[Instruction]) -> Self:
+        """Add instructions to the ir.
+
+        Args:
+            instruction: A single instruction or an iterable of instructions to append to the IR.
+
+        """
+        if isinstance(instruction, Instruction):
+            instruction = [instruction]
+        for instr in instruction:
+            self._check_out_of_bounds_access(instr)
+            self.ir.add_statement(instr)
+        return self
+
     def to_circuit(self) -> Circuit:
         """Build the circuit.
 

tests/test_circuit_builder.py

@@ -548,3 +548,84 @@ def test_sgmq_length_mismatch(self) -> None:
 
         with pytest.raises(ValueError, match="SGMQ requires matching operand lengths: got 3 and 2"):
             builder.CNOT([0, 1, 2], [1, 2])
+
+
+class TestAddInstruction:
+    def test_add_single_instruction(self) -> None:
+        builder = CircuitBuilder(2)
+        builder.add_instruction(H(0))
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == [H(0)]
+
+    def test_add_multiple_instructions(self) -> None:
+        builder = CircuitBuilder(2)
+        builder.add_instruction([H(0), CNOT(0, 1)])
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == [H(0), CNOT(0, 1)]
+
+    def test_add_multiple_parametric_instructions(self) -> None:
+        builder = CircuitBuilder(4)
+        builder.add_instruction(Rz(i, pi / 2 ** (i + 1)) for i in range(4))
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == [Rz(i, pi / 2 ** (i + 1)) for i in range(4)]
+
+    def test_add_instruction_chaining(self) -> None:
+        builder = CircuitBuilder(2)
+        circuit = builder.add_instruction(H(0)).add_instruction(CNOT(0, 1)).to_circuit()
+
+        assert circuit.ir.statements == [H(0), CNOT(0, 1)]
+
+    def test_add_instruction_mixed_with_plain_builder_calls(self) -> None:
+        builder = CircuitBuilder(3)
+        builder.H(0)
+        builder.add_instruction(CNOT(0, 1))
+        builder.H(2)
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == [H(0), CNOT(0, 1), H(2)]
+
+    def test_add_instruction_out_of_bounds_qubit(self) -> None:
+        builder = CircuitBuilder(2)
+
+        with pytest.raises(IndexError, match="qubit index 5 is out of bounds"):
+            builder.add_instruction(H(5))
+
+    def test_add_instruction_out_of_bounds_bit(self) -> None:
+        builder = CircuitBuilder(2, 2)
+
+        with pytest.raises(IndexError, match="bit index 10 is out of bounds"):
+            builder.add_instruction(Measure(0, 10))
+
+    def test_add_empty_list(self) -> None:
+        builder = CircuitBuilder(2)
+        builder.add_instruction([])
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == []
+
+    @pytest.mark.parametrize(
+        ("instruction", "expected"),
+        [
+            (Measure(0, 0), Measure(0, 0)),
+            (Init(0), Init(0)),
+            (Reset(0), Reset(0)),
+            (Barrier(0), Barrier(0)),
+            (Wait(0, 10), Wait(0, 10)),
+        ],
+        ids=[
+            "measure",
+            "init",
+            "reset",
+            "barrier",
+            "wait",
+        ],
+    )
+    def test_add_instruction_non_unitaries(self, instruction: Instruction, expected: Instruction) -> None:
+        builder = CircuitBuilder(2, 2)
+        builder.add_instruction(instruction)
+        circuit = builder.to_circuit()
+
+        assert circuit.ir.statements == [expected]