Update fmod module of math

- Implement fmod function with test case

Author: johan.park

tests/snippets/stdlib_math.py

@@ -246,3 +246,23 @@ def assertAllNotClose(examples, *args, **kwargs):
 modf_nan = math.modf(NAN)
 assert math.isnan(modf_nan[0])
 assert math.isnan(modf_nan[1])
+
+assert math.fmod(10, 1) == 0.0
+assert math.fmod(10, 0.5) == 0.0
+assert math.fmod(10, 1.5) == 1.0
+assert math.fmod(-10, 1) == -0.0
+assert math.fmod(-10, 0.5) == -0.0
+assert math.fmod(-10, 1.5) == -1.0
+assert math.isnan(math.fmod(NAN, 1.)) == True
+assert math.isnan(math.fmod(1., NAN)) == True
+assert math.isnan(math.fmod(NAN, NAN)) == True
+assert_raises(ValueError, lambda: math.fmod(1., 0.))
+assert_raises(ValueError, lambda: math.fmod(INF, 1.))
+assert_raises(ValueError, lambda: math.fmod(NINF, 1.))
+assert_raises(ValueError, lambda: math.fmod(INF, 0.))
+assert math.fmod(3.0, INF) == 3.0
+assert math.fmod(-3.0, INF) == -3.0
+assert math.fmod(3.0, NINF) == 3.0
+assert math.fmod(-3.0, NINF) == -3.0
+assert math.fmod(0.0, 3.0) == 0.0
+assert math.fmod(0.0, NINF) == 0.0

vm/src/stdlib/math.rs

@@ -275,6 +275,20 @@ fn math_modf(x: IntoPyFloat, _vm: &VirtualMachine) -> (f64, f64) {
     (x.fract(), x.trunc())
 }
 
+fn math_fmod(x: IntoPyFloat, y: IntoPyFloat, vm: &VirtualMachine) -> PyResult<f64> {
+    let x = x.to_f64();
+    let y = y.to_f64();
+    if y.is_infinite() && x.is_finite() {
+        return Ok(x);
+    }
+    let r = x % y;
+    if r.is_nan() && !x.is_nan() && !y.is_nan() {
+        return Err(vm.new_value_error("math domain error".to_string()));
+    }
+
+    Ok(r)
+}
+
 pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
     let ctx = &vm.ctx;
 
@@ -327,6 +341,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
         "frexp" => ctx.new_rustfunc(math_frexp),
         "ldexp" => ctx.new_rustfunc(math_ldexp),
         "modf" => ctx.new_rustfunc(math_modf),
+        "fmod" => ctx.new_rustfunc(math_fmod),
 
         // Rounding functions:
         "trunc" => ctx.new_rustfunc(math_trunc),