reval 0.1.3

Simple Rust expression evaluator
Documentation 
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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155

use std::str::FromStr;

use crate::value::Value;
use nom::{
    branch::alt,
    bytes::complete::{is_not, tag},
    character::complete::{char, digit0, digit1},
    combinator::{map, map_res, opt, recognize},
    sequence::{delimited, pair, tuple},
    IResult,
};

pub fn value(input: &str) -> IResult<&str, Value> {
    alt((
        bool_value,
        alt((float_value, alt((int_value, string_value)))),
    ))(input)
}

fn int_value(input: &str) -> IResult<&str, Value> {
    map(map_res(recognize_int, str::parse), Value::Int)(input)
}

fn recognize_int(input: &str) -> IResult<&str, &str> {
    recognize(map(pair(opt(alt((char('+'), char('-')))), digit1), |_| ()))(input)
}

#[cfg(test)]
mod when_parsing_integer_value {
    use super::*;

    #[test]
    fn should_parse_integer() {
        assert_eq!(value("15").unwrap().1, Value::Int(15));
    }

    #[test]
    fn should_parse_negative_integer() {
        assert_eq!(value("-6").unwrap().1, Value::Int(-6))
    }
}

fn float_value(input: &str) -> IResult<&str, Value> {
    map(map_res(recognize_float, str::parse), Value::Float)(input)
}

fn recognize_float(input: &str) -> IResult<&str, &str> {
    recognize(tuple((
        opt(alt((char('+'), char('-')))),
        alt((
            map(tuple((digit0, char('.'), digit1)), |_| ()),
            map(tuple((char('.'), digit1)), |_| ()),
        )),
        opt(tuple((
            alt((char('e'), char('E'))),
            opt(alt((char('+'), char('-')))),
            digit1,
        ))),
    )))(input)
}

#[cfg(test)]
mod when_parsing_float_value {
    use super::*;

    #[test]
    fn should_parse_simple_float() {
        assert_eq!(value("5.0").unwrap().1, Value::Float(5.0));
    }

    #[test]
    fn should_parse_negative_float() {
        assert_eq!(value("-5.0").unwrap().1, Value::Float(-5.0));
    }

    #[test]
    fn should_parse_exponent() {
        assert_eq!(value("38.0e-1").unwrap().1, Value::Float(3.8))
    }
}

fn bool_value(input: &str) -> IResult<&str, Value> {
    map(
        map_res(alt((tag("true"), tag("false"))), FromStr::from_str),
        Value::Bool,
    )(input)
}

#[cfg(test)]
mod when_parsing_bool_value {
    use super::*;

    #[test]
    fn should_parse_true() {
        assert_eq!(bool_value("true").unwrap().1, Value::Bool(true));
        // assert_eq!(bool_value("true").unwrap().1, Value::Bool(true));
    }

    #[test]
    fn should_parse_false() {
        assert_eq!(bool_value("false").unwrap().1, Value::Bool(false));
    }

    #[test]
    fn should_not_parse_non_bool() {
        assert!(bool_value("stuff").is_err());
    }
}

fn string_value(input: &str) -> IResult<&str, Value> {
    map(
        alt((
            delimited(char('"'), is_not("\""), char('"')),
            delimited(char('\''), is_not("'"), char('\'')),
        )),
        |value: &str| Value::String(value.to_string()),
    )(input)
}

#[cfg(test)]
mod when_parsing_string_value {
    use super::*;

    #[test]
    fn should_parse_double_quoted_string() {
        assert_eq!(
            string_value("\"string value\"").unwrap().1,
            Value::String("string value".to_string())
        );
    }

    #[test]
    fn should_ignore_single_quotes_inside_double_quoted_string() {
        assert_eq!(
            string_value("\"string 'value'\"").unwrap().1,
            Value::String("string 'value'".to_string())
        );
    }

    #[test]
    fn should_parse_single_quoted_string() {
        assert_eq!(
            string_value("'string value'").unwrap().1,
            Value::String("string value".to_string())
        );
    }

    #[test]
    fn should_ignore_double_quotes_inside_single_quoted_string() {
        assert_eq!(
            string_value("'string \"value\"'").unwrap().1,
            Value::String("string \"value\"".to_string())
        );
    }
}