From 725025e12eaac58255f83ab24491c30c7cc1dfde Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <b.schoenmaeckers@zandersgroup.com>
Date: Thu, 21 May 2026 08:45:21 +0200
Subject: [PATCH] Add complex number support to c-api

---
 Cargo.lock                       |  1 +
 crates/capi/Cargo.toml           |  1 +
 crates/capi/src/complexobject.rs | 52 ++++++++++++++++++++++++++++++++
 crates/capi/src/lib.rs           |  1 +
 4 files changed, 55 insertions(+)
 create mode 100644 crates/capi/src/complexobject.rs

diff --git a/Cargo.lock b/Cargo.lock
index b1fe77d955..eab7707b5b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3231,6 +3231,7 @@ dependencies = [
 name = "rustpython-capi"
 version = "0.5.0"
 dependencies = [
+ "num-complex",
  "pyo3",
  "rustpython-stdlib",
  "rustpython-vm",
diff --git a/crates/capi/Cargo.toml b/crates/capi/Cargo.toml
index 85f42934a9..8c54a8b26a 100644
--- a/crates/capi/Cargo.toml
+++ b/crates/capi/Cargo.toml
@@ -12,6 +12,7 @@ license.workspace = true
 crate-type = ["cdylib", "rlib"]
 
 [dependencies]
+num-complex = { workspace = true }
 rustpython-vm = { workspace = true, features = ["threading", "compiler"] }
 rustpython-stdlib = {workspace = true, features = ["threading"] }
 
diff --git a/crates/capi/src/complexobject.rs b/crates/capi/src/complexobject.rs
new file mode 100644
index 0000000000..a6b2bb731a
--- /dev/null
+++ b/crates/capi/src/complexobject.rs
@@ -0,0 +1,52 @@
+use crate::object::define_py_check;
+use crate::{PyObject, pystate::with_vm};
+use core::ffi::c_double;
+use num_complex::{Complex, Complex64};
+use rustpython_vm::builtins::PyComplex;
+use rustpython_vm::{PyResult, VirtualMachine};
+
+define_py_check!(fn PyComplex_Check, types.complex_type);
+define_py_check!(exact fn PyComplex_CheckExact, types.complex_type);
+
+#[unsafe(no_mangle)]
+pub extern "C" fn PyComplex_FromDoubles(real: c_double, imag: c_double) -> *mut PyObject {
+    with_vm(|vm| vm.ctx.new_complex(Complex::new(real, imag)))
+}
+
+fn try_to_complex(vm: &VirtualMachine, obj: &PyObject) -> PyResult<Complex64> {
+    obj.try_downcast_ref::<PyComplex>(vm).map_or_else(
+        |type_err| {
+            if let Some((complex, _)) = obj.to_owned().try_complex(vm)? {
+                Ok(complex)
+            } else {
+                Err(type_err)
+            }
+        },
+        |complex| Ok(complex.to_complex()),
+    )
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyComplex_RealAsDouble(obj: *mut PyObject) -> c_double {
+    with_vm(|vm| try_to_complex(vm, unsafe { &*obj }).map(|complex| complex.re))
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyComplex_ImagAsDouble(obj: *mut PyObject) -> c_double {
+    with_vm(|vm| try_to_complex(vm, unsafe { &*obj }).map(|complex| complex.im))
+}
+
+#[cfg(false)]
+mod tests {
+    use pyo3::prelude::*;
+    use pyo3::types::PyComplex;
+
+    #[test]
+    fn test_py_int() {
+        Python::attach(|py| {
+            let number = PyComplex::from_doubles(py, 1.0, 2.0);
+            assert_eq!(number.real(), 1.0);
+            assert_eq!(number.imag(), 2.0);
+        })
+    }
+}
diff --git a/crates/capi/src/lib.rs b/crates/capi/src/lib.rs
index baa4ddc6b7..c69a9299fe 100644
--- a/crates/capi/src/lib.rs
+++ b/crates/capi/src/lib.rs
@@ -12,6 +12,7 @@ pub mod abstract_;
 pub mod boolobject;
 pub mod bytesobject;
 pub mod ceval;
+pub mod complexobject;
 pub mod dictobject;
 pub mod import;
 pub mod longobject;