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Convert math.ldexp()'s x like any float argument and read float subclasses directly #9520

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Merged
youknowone merged 2 commits into from
Nov 1, 2026
Merged

Convert math.ldexp()'s x like any float argument and read float subclasses directly #9520

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315dbb7
Convert the math.ldexp() mantissa like any float argument
jseop-lim Nov 1, 2026
83c315e
Read a float subclass directly in ArgIntoFloat
jseop-lim Nov 1, 2026
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15 changes: 5 additions & 10 deletions crates/stdlib/src/math.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,13 +6,11 @@ use crate::vm::{VirtualMachine, builtins::PyBaseExceptionRef};
#[pymodule]
mod math {
use crate::vm::{
AsObject, Py, PyObject, PyObjectRef, PyRef, PyResult, VirtualMachine,
AsObject, Py, PyObject, PyObjectRef, PyResult, VirtualMachine,
builtins::{
PyFloat, PyInt, PyIntRef, PyModule, PyStrInterned, try_bigint_to_f64, try_f64_to_bigint,
},
function::{
ArgIndex, ArgIntoFloat, ArgIterable, Either, NameCoordinates, OptionalArg, PosArgs,
},
function::{ArgIndex, ArgIntoFloat, ArgIterable, NameCoordinates, OptionalArg, PosArgs},
identifier,
};
use malachite_bigint::BigInt;
Expand Down Expand Up @@ -457,7 +455,7 @@ mod math {
#[derive(FromArgs)]
struct LdexpArgs {
#[pyarg(positional)]
x: Either<PyRef<PyFloat>, PyIntRef>,
x: ArgIntoFloat,
// Refuses anything that is not an `int`, including objects with `__index__`.
#[pyarg(positional, error_msg = "Expected an int as second argument to ldexp.")]
i: PyIntRef,
Expand All @@ -466,11 +464,8 @@ mod math {
#[pyfunction]
fn ldexp(args: LdexpArgs, vm: &VirtualMachine) -> PyResult<f64> {
let LdexpArgs { x, i } = args;
let value = match x {
Either::A(f) => f.to_f64(),
Either::B(z) => try_bigint_to_f64(z.as_bigint(), vm)?,
};
pymath::math::ldexp_bigint(value, i.as_bigint()).map_err(|err| pymath_exception(err, vm))
pymath::math::ldexp_bigint(x.into_float(), i.as_bigint())
.map_err(|err| pymath_exception(err, vm))
}

#[pyfunction]
Expand Down
8 changes: 7 additions & 1 deletion crates/vm/src/function/number.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use super::argument::OptionalArg;
use crate::{
AsObject, Py, PyObjectRef, PyResult, TryFromObject, VirtualMachine,
builtins::{PyInt, PyIntRef},
builtins::{PyFloat, PyInt, PyIntRef},
};
use core::ops::Deref;
use malachite_bigint::BigInt;
Expand Down Expand Up @@ -88,6 +88,12 @@ impl From<ArgIntoFloat> for f64 {
impl TryFromObject for ArgIntoFloat {
// Equivalent to PyFloat_AsDouble.
fn try_from_object(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<Self> {
// A float subclass is read directly, without calling its __float__.
if let Some(float) = obj.downcast_ref::<PyFloat>() {
return Ok(Self {
value: float.to_f64(),
});
}
let value = obj.try_float(vm)?.to_f64();
Ok(Self { value })
}
Expand Down
30 changes: 30 additions & 0 deletions extra_tests/snippets/stdlib_math.py
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Expand Up @@ -541,3 +541,33 @@ def assertAllNotClose(examples, *args, **kwargs):
assert math.perm(5) == math.perm(5, None) == 120
assert math.perm(2**64, 0) == 1
assert math.comb(2**64, 2**64 - 1) == 2**64


class LdexpFloat:
def __float__(self):
return 1.5


class LdexpIndex:
def __index__(self):
return 3


class LdexpRaisingFloat:
def __float__(self):
raise RuntimeError


assert math.ldexp(LdexpFloat(), 1) == 3.0

@chatgpt-codex-connector chatgpt-codex-connector Bot Nov 1, 2026

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P1 Badge Honor the restriction on modifying existing test files

This regression block adds new test logic and assertions to an existing test file, whereas the root AGENTS.md explicitly limits test-file modifications to adding/removing @unittest.expectedFailure decorators and removing associated TODO comments. Revert these additions or obtain an explicit exception before including them, since they fall outside the permitted test-change scope.

AGENTS.md reference: AGENTS.md:L280-L282

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@jseop-lim jseop-lim Nov 1, 2026

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That section covers the CPython tests in Lib/test. For extra_tests/snippets, AGENTS.md asks for new tests in the most closely related existing file (L119-L120), which is what this does. None of these cases is in Lib/test/test_math.py: testLdexp only passes int and float mantissas.

assert math.ldexp(LdexpIndex(), 1) == 6.0
assert_raises(RuntimeError, math.ldexp, LdexpRaisingFloat(), 1)
assert_raises(OverflowError, math.ldexp, 10**400, 1)


class FloatSubclass(float):
def __float__(self):
return 9.0


assert math.sqrt(FloatSubclass(4.0)) == 2.0
assert math.ldexp(FloatSubclass(1.0), 1) == 2.0
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