Improve float.fromhex module of objfloat (#1552)

* Improve  float.fromhex module of objfloat

- Python float.fromhex can handle string of float and hex without `.`
  - For example '0.0', '-0.0', '0x0p0', '-0x0p0'
- Add test case mantioned

* Change unwrap to expect for error handling

* Improve error handling with pattern matching

- `expect` that can't express python vm error message changed to pattern match
- Erase duplicated test case

* Refactoring with or_else and map_err

- Use `or_else` instead of value condition and `match` statement
  - For floating-point input
- Use `map_err` instead of `match ` statement
  - For hexadecimal floating-point input without dot

* Add else condition

tests/snippets/floats.py

@@ -240,12 +240,21 @@ a = 3.1__4
 with assert_raises(SyntaxError):
     exec(src)
 
+assert float.fromhex('0.0') == 0.0
+assert float.fromhex('-0.0') == 0.0
+assert float.fromhex('0x0p0') == 0.0
+assert float.fromhex('0x010p0') == 16.0
+assert float.fromhex('0x0.10p3') == 0.5
+assert float.fromhex('-0x0p0') == 0.0
+assert float.fromhex('0x0.p0') == 0.0
+assert float.fromhex('-0x0.p0') == 0.0
 assert float.fromhex('0x0.0p+0') == 0.0
 assert float.fromhex('-0x0.0p+0') == -0.0
 assert float.fromhex('0x1.000000p+0') == 1.0
 assert float.fromhex('-0x1.800000p+0') == -1.5
 assert float.fromhex('inf') == float('inf')
 assert math.isnan(float.fromhex('nan'))
+assert_raises(ValueError, lambda: float.fromhex('error'))
 
 assert (0.0).hex() == '0x0.0p+0'
 assert (-0.0).hex() == '-0x0.0p+0'

vm/src/obj/objfloat.rs

@@ -583,12 +583,30 @@ impl PyFloat {
 
     #[pymethod]
     fn fromhex(repr: PyStringRef, vm: &VirtualMachine) -> PyResult<f64> {
-        hexf_parse::parse_hexf64(repr.as_str(), false).or_else(|_| match repr.as_str() {
-            "nan" => Ok(std::f64::NAN),
-            "inf" => Ok(std::f64::INFINITY),
-            "-inf" => Ok(std::f64::NEG_INFINITY),
-            _ => Err(vm.new_value_error("invalid hexadecimal floating-point string".to_string())),
-        })
+        hexf_parse::parse_hexf64(repr.as_str(), false)
+            .or_else(|_| repr.as_str().parse::<f64>())
+            .or_else(|_| match repr.as_str() {
+                "nan" => Ok(std::f64::NAN),
+                "inf" => Ok(std::f64::INFINITY),
+                "-inf" => Ok(std::f64::NEG_INFINITY),
+                value => {
+                    let mut hex = String::new();
+                    if value.contains("0x") {
+                        for ch in value.chars() {
+                            if ch == 'p' {
+                                hex.push_str(".p");
+                            } else {
+                                hex.push(ch);
+                            }
+                        }
+                    } else {
+                        hex = value.to_string();
+                    }
+                    hexf_parse::parse_hexf64(hex.as_str(), false).map_err(|_| {
+                        vm.new_value_error("invalid hexadecimal floating-point string".to_string())
+                    })
+                }
+            })
     }
 
     #[pymethod]