math: Implement math.nextafter

tests/snippets/stdlib_math.py

@@ -240,6 +240,19 @@ assert math.factorial(10) == 3628800
 assert math.factorial(20) == 2432902008176640000
 assert_raises(ValueError, lambda: math.factorial(-1))
 
+if hasattr(math, 'nextafter'):
+    try:
+        assert math.nextafter(4503599627370496.0, -INF) == 4503599627370495.5
+        assert math.nextafter(4503599627370496.0, INF) == 4503599627370497.0
+        assert math.nextafter(9223372036854775808.0, 0.0) == 9223372036854774784.0
+        assert math.nextafter(-9223372036854775808.0, 0.0) == -9223372036854774784.0
+        assert math.nextafter(4503599627370496, -INF) == 4503599627370495.5
+        assert math.nextafter(2.0, 2.0) == 2.0
+        assert math.isnan(math.nextafter(NAN, 1.0))
+    except NotImplementedError:
+        # WASM
+        pass
+
 assert math.modf(1.25) == (0.25, 1.0)
 assert math.modf(-1.25) == (-0.25, -1.0)
 assert math.modf(2.56) == (0.56, 2.0)

vm/src/stdlib/math.rs

@@ -17,6 +17,9 @@ use crate::obj::objtype;
 use crate::pyobject::{PyObjectRef, PyResult, TypeProtocol};
 use crate::vm::VirtualMachine;
 
+#[cfg(not(target_arch = "wasm32"))]
+use libc::c_double;
+
 use std::cmp::Ordering;
 
 // Helper macro:
@@ -291,6 +294,21 @@ fn math_modf(x: IntoPyFloat, _vm: &VirtualMachine) -> (f64, f64) {
     (x.fract(), x.trunc())
 }
 
+#[cfg(not(target_arch = "wasm32"))]
+fn math_nextafter(x: IntoPyFloat, y: IntoPyFloat) -> PyResult<f64> {
+    extern "C" {
+        fn nextafter(x: c_double, y: c_double) -> c_double;
+    }
+    let x = x.to_f64();
+    let y = y.to_f64();
+    Ok(unsafe { nextafter(x, y) })
+}
+
+#[cfg(target_arch = "wasm32")]
+fn math_nextafter(x: IntoPyFloat, y: IntoPyFloat, vm: &VirtualMachine) -> PyResult<f64> {
+    Err(vm.new_not_implemented_error("not implemented for this platform".to_string()))
+}
+
 fn fmod(x: f64, y: f64) -> f64 {
     if y.is_infinite() && x.is_finite() {
         return x;
@@ -415,6 +433,8 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         // Factorial function
         "factorial" => ctx.new_rustfunc(math_factorial),
 
+        "nextafter" => ctx.new_rustfunc(math_nextafter),
+
         // Constants:
         "pi" => ctx.new_float(std::f64::consts::PI), // 3.14159...
         "e" => ctx.new_float(std::f64::consts::E), // 2.71..