Consider cases when ExpressionConvertible returns float, int, duration (

#89)

* consider case when ExpressionConvertible returns float, int, duration

* use to_ast to create the ast node after _to_oqpy_expression

* allow use of str in OQPyBinaryExpression

* change type hints

* black

---------

Co-authored-by: Phil Reinhold <[email protected]>

oqpy/base.py

@@ -338,7 +338,7 @@ def expr_matches(a: Any, b: Any) -> bool:
 class ExpressionConvertible(Protocol):
     """This is the protocol an object can implement in order to be usable as an expression."""
 
-    def _to_oqpy_expression(self) -> HasToAst: ...  # pragma: no cover
+    def _to_oqpy_expression(self) -> AstConvertible: ...  # pragma: no cover
 
 
 @runtime_checkable
@@ -379,12 +379,17 @@ class OQPyBinaryExpression(OQPyExpression):
 
     def __init__(
         self,
-        op: ast.BinaryOperator,
+        op: ast.BinaryOperator | str,
         lhs: AstConvertible,
         rhs: AstConvertible,
         ast_type: ast.ClassicalType | None = None,
     ):
         super().__init__()
+        if isinstance(op, str):
+            try:
+                op = ast.BinaryOperator[op]
+            except KeyError as e:
+                raise ValueError(f"Invalid binary operator {op}") from e
         self.op = op
         self.lhs = lhs
         self.rhs = rhs
@@ -396,7 +401,9 @@ def __init__(
             elif isinstance(rhs, OQPyExpression):
                 ast_type = rhs.type
             else:
-                raise TypeError("Neither lhs nor rhs is an expression?")
+                raise TypeError(
+                    "Cannot infer ast_type from lhs or rhs. Please provide it if possible."
+                )
         self.type = ast_type
 
         # Adding floats to durations is not allowed. So we promote types as necessary.
@@ -468,17 +475,14 @@ def to_ast(self, program: Program) -> ast.Expression:
 def to_ast(program: Program, item: AstConvertible) -> ast.Expression:
     """Convert an object to an AST node."""
     if hasattr(item, "_to_oqpy_expression"):
-        item = cast(ExpressionConvertible, item)
-        return item._to_oqpy_expression().to_ast(program)
+        item = cast(ExpressionConvertible, item)._to_oqpy_expression()
     if hasattr(item, "_to_cached_oqpy_expression"):
         item = cast(CachedExpressionConvertible, item)
         if item._oqpy_cache_key is None:
             item._oqpy_cache_key = uuid.uuid1()
         if item._oqpy_cache_key not in program.expr_cache:
-            program.expr_cache[item._oqpy_cache_key] = item._to_cached_oqpy_expression().to_ast(
-                program
-            )
-        return program.expr_cache[item._oqpy_cache_key]
+            program.expr_cache[item._oqpy_cache_key] = item._to_cached_oqpy_expression()
+        item = program.expr_cache[item._oqpy_cache_key]
     if isinstance(item, (complex, np.complexfloating)):
         if item.imag == 0:
             return to_ast(program, item.real)

oqpy/timing.py

@@ -68,16 +68,16 @@ def convert_float_to_duration(time: AstConvertible, require_nonnegative: bool =
       require_nonnegative: if True, raise an exception if the time value is known to
         be negative.
     """
-    if isinstance(time, (float, int)):
-        if require_nonnegative and time < 0:
-            raise ValueError(f"Expected a non-negative duration, but got {time}")
-        return OQDurationLiteral(time)
     if hasattr(time, "_to_oqpy_expression"):
         time = cast(ExpressionConvertible, time)
         time = time._to_oqpy_expression()
     if hasattr(time, "_to_cached_oqpy_expression"):
         time = cast(CachedExpressionConvertible, time)
         time = time._to_cached_oqpy_expression()
+    if isinstance(time, (float, int)):
+        if require_nonnegative and time < 0:
+            raise ValueError(f"Expected a non-negative duration, but got {time}")
+        return OQDurationLiteral(time)
     if isinstance(time, OQPyExpression):
         if isinstance(time.type, (ast.UintType, ast.IntType, ast.FloatType)):
             time = time * OQDurationLiteral(1)

tests/test_directives.py

@@ -30,7 +30,7 @@
 
 import oqpy
 from oqpy import *
-from oqpy.base import OQPyExpression, expr_matches, logical_and, logical_or
+from oqpy.base import OQPyBinaryExpression, OQPyExpression, expr_matches, logical_and, logical_or
 from oqpy.classical_types import OQIndexExpression
 from oqpy.quantum_types import PhysicalQubits
 from oqpy.timing import OQDurationLiteral
@@ -421,6 +421,7 @@ def test_binary_expressions():
     prog.set(d, 5e-9 - d)
     prog.set(d, d + convert_float_to_duration(10e-9))
     prog.set(f, d / convert_float_to_duration(1))
+    prog.set(k, OQPyBinaryExpression("+", 2, k))
 
     with pytest.raises(ValueError):
         prog.set(f, "a" * i)
@@ -436,6 +437,8 @@ def test_binary_expressions():
         prog.set(d, 5j / d)
     with pytest.raises(TypeError):
         prog.set(d, 5j * d)
+    with pytest.raises(ValueError):
+        OQPyBinaryExpression(".", d, d)
 
     expected = textwrap.dedent(
         """
@@ -479,6 +482,7 @@ def test_binary_expressions():
         d = 5.0ns - d;
         d = d + 10.0ns;
         f = d / 1s;
+        k = 2 + k;
         """
     ).strip()
 
@@ -1583,21 +1587,34 @@ class B:
         def _to_oqpy_expression(self):
             return FloatVar(1e-7, self.name)
 
+    @dataclass
+    class C:
+        def _to_oqpy_expression(self):
+            return 1e-7
+
+        def __rmul__(self, other):
+            return other * self._to_oqpy_expression()
+
     frame = FrameVar(name="f1")
     prog = Program()
     prog.set(A("a1"), 2)
+    prog.set(FloatVar(name="c1"), 3 * C())
     prog.delay(A("a2"), frame)
     prog.delay(B("b1"), frame)
+    prog.delay(C(), frame)
     expected = textwrap.dedent(
         """
         OPENQASM 3.0;
         duration a1 = 100.0ns;
+        float[64] c1;
         duration a2 = 100.0ns;
         frame f1;
         float[64] b1 = 1e-07;
         a1 = 2;
+        c1 = 3e-07;
         delay[a2] f1;
         delay[b1 * 1s] f1;
+        delay[100.0ns] f1;
         """
     ).strip()
     assert prog.to_qasm() == expected