artichoke_backend/convert/
float_to_int.rs

1use spinoso_exception::{FloatDomainError, RangeError};
2
3use crate::error::Error;
4
5/// Convert a [`f64`] to an [`i64`] by rounding toward zero.
6///
7/// # Errors
8///
9/// This function can return either a [`FloatDomainError`] or a [`RangeError`].
10///
11/// [`FloatDomainError`] is returned if the input is either [`NaN`] or infinite.
12///
13/// [`RangeError`] is returned if the input is finite but out of range of
14/// `i64::MIN..=i64::MAX`.
15///
16/// [`NaN`]: f64::NAN
17#[expect(
18    clippy::cast_possible_truncation,
19    clippy::cast_precision_loss,
20    reason = "XXX: explain reason - https://github.com/artichoke/artichoke/pull/2813"
21)]
22pub fn float_to_int(float: f64) -> Result<i64, Error> {
23    if float.is_nan() {
24        return Err(FloatDomainError::with_message("NaN").into());
25    }
26    if float.is_sign_negative() {
27        if float.is_infinite() {
28            return Err(FloatDomainError::with_message("-Infinity").into());
29        }
30        // ```
31        // [3.1.2] > Integer -10.9
32        // => -10
33        // [3.1.2] > Integer -10.5
34        // => -10
35        // [3.1.2] > Integer -10.2
36        // => -10
37        // ```
38        let float = float.ceil();
39        if float < i64::MIN as f64 {
40            return Err(RangeError::with_message("too small for int").into());
41        }
42        Ok(float as i64)
43    } else {
44        if float.is_infinite() {
45            return Err(FloatDomainError::with_message("Infinity").into());
46        }
47        // ```
48        // [3.1.2] > Integer 10.9
49        // => 10
50        // [3.1.2] > Integer 10.5
51        // => 10
52        // [3.1.2] > Integer 10.2
53        // => 10
54        // ```
55        let float = float.floor();
56        if float > i64::MAX as f64 {
57            return Err(RangeError::with_message("too big for int").into());
58        }
59        Ok(float as i64)
60    }
61}
62
63#[cfg(test)]
64mod tests {
65    use bstr::ByteSlice;
66
67    use super::float_to_int;
68    use crate::test::prelude::*;
69
70    #[test]
71    fn float_to_int_rounds_to_zero() {
72        let result = float_to_int(10.0).unwrap();
73        assert_eq!(result, 10);
74        let result = float_to_int(10.2).unwrap();
75        assert_eq!(result, 10);
76        let result = float_to_int(10.5).unwrap();
77        assert_eq!(result, 10);
78        let result = float_to_int(10.9).unwrap();
79        assert_eq!(result, 10);
80
81        let result = float_to_int(-10.0).unwrap();
82        assert_eq!(result, -10);
83        let result = float_to_int(-10.2).unwrap();
84        assert_eq!(result, -10);
85        let result = float_to_int(-10.5).unwrap();
86        assert_eq!(result, -10);
87        let result = float_to_int(-10.9).unwrap();
88        assert_eq!(result, -10);
89    }
90
91    #[test]
92    fn float_nan_is_domain_error() {
93        let err = float_to_int(f64::NAN).unwrap_err();
94        assert_eq!(err.message().as_bstr(), b"NaN".as_bstr());
95        assert_eq!(err.name(), "FloatDomainError");
96    }
97
98    #[test]
99    fn float_infinities_are_domain_error() {
100        let err = float_to_int(f64::INFINITY).unwrap_err();
101        assert_eq!(err.message().as_bstr(), b"Infinity".as_bstr());
102        assert_eq!(err.name(), "FloatDomainError");
103
104        let err = float_to_int(f64::NEG_INFINITY).unwrap_err();
105        assert_eq!(err.message().as_bstr(), b"-Infinity".as_bstr());
106        assert_eq!(err.name(), "FloatDomainError");
107    }
108
109    // FIXME: MRI converts these to `BigNum`s.
110    #[test]
111    fn float_out_of_i64_range_is_range_error() {
112        let err = float_to_int(f64::MAX).unwrap_err();
113        assert_eq!(err.name(), "RangeError");
114
115        let err = float_to_int(f64::MIN).unwrap_err();
116        assert_eq!(err.name(), "RangeError");
117    }
118}
artichoke_backend/convert/float_to_int.rs

artichoke_backend/convert/
float_to_int.rs
