logo
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use crate::extn::core::integer::Integer;
use crate::extn::prelude::*;

pub mod mruby;

#[derive(Debug, Clone, Copy)]
pub struct Numeric;

#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
pub enum Outcome {
    Float(f64),
    Integer(i64),
    // TODO: Complex? Rational?
}

impl ConvertMut<Outcome, Value> for Artichoke {
    fn convert_mut(&mut self, from: Outcome) -> Value {
        match from {
            Outcome::Float(num) => self.convert_mut(num),
            Outcome::Integer(num) => self.convert(num),
        }
    }
}

const MAX_COERCE_DEPTH: u8 = 15;

#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
pub enum Coercion {
    Float(f64, f64),
    Integer(i64, i64),
    // TODO: Complex? Rational?
}

/// If `y` is the same type as `x`, returns an array `[y, x]`. Otherwise,
/// returns an array with both `y` and `x` represented as `Float` objects.
///
/// This coercion mechanism is used by Ruby to handle mixed-type numeric
/// operations: it is intended to find a compatible common type between the two
/// operands of the operator.
///
/// See [`Numeric#coerce`][numeric].
///
/// # Coercion enum
///
/// Artichoke represents the `[y, x]` tuple Array as the [`Coercion`] enum, which
/// orders its values `Coercion::Integer(x, y)`.
///
/// # Examples
///
/// ```
/// # use artichoke_backend::prelude::*;
/// # use artichoke_backend::extn::core::numeric::{self, Coercion};
/// # fn example() -> Result<(), Box<dyn std::error::Error>> {
/// # let mut interp = artichoke_backend::interpreter()?;
/// let x = interp.convert(1_i64);
/// let y = interp.convert_mut(2.5_f64);
/// assert_eq!(Coercion::Float(1.0, 2.5), numeric::coerce(&mut interp, x, y)?);
/// let x = interp.convert_mut(1.2_f64);
/// let y = interp.convert(3_i64);
/// assert_eq!(Coercion::Float(1.2, 3.0), numeric::coerce(&mut interp, x, y)?);
/// let x = interp.convert(1_i64);
/// let y = interp.convert(2_i64);
/// assert_eq!(Coercion::Integer(1, 2), numeric::coerce(&mut interp, x, y)?);
/// # Ok(())
/// # }
/// # example().unwrap();
/// ```
///
/// [numeric]: https://ruby-doc.org/core-2.6.3/Numeric.html#method-i-coerce
pub fn coerce(interp: &mut Artichoke, x: Value, y: Value) -> Result<Coercion, Error> {
    fn do_coerce(interp: &mut Artichoke, x: Value, y: Value, depth: u8) -> Result<Coercion, Error> {
        if depth > MAX_COERCE_DEPTH {
            return Err(SystemStackError::with_message("stack level too deep").into());
        }
        match (x.ruby_type(), y.ruby_type()) {
            (Ruby::Float, Ruby::Float) => Ok(Coercion::Float(
                x.try_convert_into(interp)?,
                y.try_convert_into(interp)?,
            )),
            (Ruby::Float, Ruby::Fixnum) => {
                let y = y.try_convert_into::<Integer>(interp)?;
                Ok(Coercion::Float(x.try_convert_into(interp)?, y.as_f64()))
            }
            (Ruby::Fixnum, Ruby::Float) => {
                let x = x.try_convert_into::<Integer>(interp)?;
                Ok(Coercion::Float(x.as_f64(), y.try_convert_into(interp)?))
            }
            (Ruby::Fixnum, Ruby::Fixnum) => Ok(Coercion::Integer(
                x.try_convert_into(interp)?,
                y.try_convert_into(interp)?,
            )),
            _ => {
                let class_of_numeric = interp
                    .class_of::<Numeric>()?
                    .ok_or_else(|| NotDefinedError::class("Numeric"))?;
                let is_a_numeric = y.funcall(interp, "is_a?", &[class_of_numeric], None)?;
                let is_a_numeric = interp.try_convert(is_a_numeric);
                if let Ok(true) = is_a_numeric {
                    if y.respond_to(interp, "coerce")? {
                        let coerced = y.funcall(interp, "coerce", &[x], None)?;
                        let coerced: Vec<Value> = interp
                            .try_convert_mut(coerced)
                            .map_err(|_| TypeError::with_message("coerce must return [x, y]"))?;
                        let mut coerced = coerced.into_iter();
                        let y = coerced
                            .next()
                            .ok_or_else(|| TypeError::with_message("coerce must return [x, y]"))?;
                        let x = coerced
                            .next()
                            .ok_or_else(|| TypeError::with_message("coerce must return [x, y]"))?;
                        if coerced.next().is_some() {
                            Err(TypeError::with_message("coerce must return [x, y]").into())
                        } else {
                            do_coerce(interp, x, y, depth + 1)
                        }
                    } else {
                        let mut message = String::from("can't convert ");
                        message.push_str(interp.inspect_type_name_for_value(y));
                        message.push_str(" into Float");
                        Err(TypeError::from(message).into())
                    }
                } else {
                    let mut message = String::from(interp.inspect_type_name_for_value(y));
                    message.push_str(" can't be coerced into Float");
                    Err(TypeError::from(message).into())
                }
            }
        }
    }
    do_coerce(interp, x, y, 0)
}