aboutsummaryrefslogtreecommitdiff
path: root/src/lisp/expr.rs
blob: acd3365a39ecc398efc9bbe6a8d4845df4243e6e (plain)
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
156
157
158
159
160
161
162
163
164
165
166
use std::{convert::TryFrom, fmt};

use crate::app::AppState;
use crate::lisp::{
    error::{EvalError, LispError},
    number::LispNumber,
};

#[derive(Clone)]
pub struct PrimitiveFunc {
    pub arity: Option<usize>, // minimim arity
    pub closure: fn(&[LispExpr], &mut AppState) -> Result<LispExpr, LispError>,
}

impl PrimitiveFunc {
    pub fn call(&self, args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
        if let Some(arity) = self.arity {
            if args.len() < arity {
                return Err(EvalError::ArgumentCount(self.arity.map(|u| u as u32)).into());
            }
        }
        (self.closure)(args, app)
    }
}

pub type Ident = String;
pub type BoolLit = bool;

#[derive(Clone)]
pub struct LispFunction {
    pub params: Vec<String>,
    pub body: Vec<LispExpr>,
}

#[derive(Clone)]
pub enum LispExpr {
    Unit,
    Number(LispNumber),
    List(Vec<LispExpr>),
    StringLit(String),
    BoolLit(bool),
    Ident(Ident),
    PrimitiveFunc(PrimitiveFunc),
    Function(LispFunction),

    // none of these depths should be zero
    Quasiquote(Box<LispExpr>, u32),
    Comma(Box<LispExpr>, u32),
    CommaAt(Box<LispExpr>, u32),
    Quote(Box<LispExpr>, u32),
}

impl LispExpr {
    pub fn comma(self, n: u32) -> LispExpr {
        match self {
            LispExpr::Comma(v, i) => LispExpr::Comma(v, i.checked_add(n).expect("comma overflow")),
            LispExpr::CommaAt(v, i) => LispExpr::CommaAt(v, i + n),
            v => LispExpr::Comma(Box::new(v), n),
        }
    }

    pub fn comma_at(self, n: u32) -> LispExpr {
        match self {
            LispExpr::CommaAt(v, i) => {
                LispExpr::CommaAt(v, i.checked_add(n).expect("comma_at overflow"))
            }
            v => LispExpr::CommaAt(Box::new(v), n),
        }
    }

    pub fn quote(self, n: u32) -> LispExpr {
        match self {
            LispExpr::Quote(v, i) => LispExpr::Quote(v, i.checked_add(n).expect("quote overflow")),
            v => LispExpr::Quote(Box::new(v), n),
        }
    }

    pub fn quasiquote(self, n: u32) -> LispExpr {
        match self {
            LispExpr::Quasiquote(v, i) => {
                LispExpr::Quasiquote(v, i.checked_add(n).expect("quasiquote overflow"))
            }
            v => LispExpr::Quasiquote(Box::new(v), n),
        }
    }
}

impl fmt::Display for LispExpr {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            LispExpr::Unit => write!(f, "()")?,
            LispExpr::Number(n) => write!(f, "{}", n)?,
            LispExpr::List(l) => {
                for expr in l.iter() {
                    write!(f, " {} ", expr)?
                }
            }
            LispExpr::StringLit(s) => write!(f, "{}", s)?,
            LispExpr::BoolLit(b) => {
                if *b {
                    write!(f, "#t")?
                } else {
                    write!(f, "#f")?
                }
            }
            LispExpr::Ident(s) => write!(f, "{}", s)?,
            LispExpr::PrimitiveFunc(_) => write!(f, "<#primitive>")?,
            LispExpr::Function(func) => write!(f, "<#lambda {}>", func.params.join(" "))?,
            LispExpr::Quasiquote(val, depth) => {
                write!(f, "{}{}", "`".repeat(*depth as usize), val)?
            }
            LispExpr::Comma(val, depth) => write!(f, "{}{}", ",".repeat(*depth as usize), val)?,
            LispExpr::CommaAt(val, depth) => write!(f, "{}@{}", ",".repeat(*depth as usize), val)?,
            LispExpr::Quote(val, depth) => write!(f, "{}{}", "'".repeat(*depth as usize), val)?,
        };
        Ok(())
    }
}

impl TryFrom<LispExpr> for LispNumber {
    type Error = LispError;
    fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
        match value {
            LispExpr::Number(i) => Ok(i),
            _ => Err(LispError::Eval(EvalError::TypeMismatch)),
        }
    }
}

impl<'a> TryFrom<&'a LispExpr> for &'a LispNumber {
    type Error = LispError;
    fn try_from(value: &'a LispExpr) -> Result<Self, Self::Error> {
        match value {
            LispExpr::Number(i) => Ok(i),
            _ => Err(LispError::Eval(EvalError::TypeMismatch)),
        }
    }
}

impl TryFrom<LispExpr> for Ident {
    type Error = LispError;
    fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
        match value {
            LispExpr::Ident(i) => Ok(i),
            _ => Err(LispError::Eval(EvalError::TypeMismatch)),
        }
    }
}

impl TryFrom<LispExpr> for BoolLit {
    type Error = LispError;
    fn try_from(value: LispExpr) -> Result<Self, Self::Error> {
        match value {
            LispExpr::BoolLit(i) => Ok(i),
            _ => Err(LispError::Eval(EvalError::TypeMismatch)),
        }
    }
}

pub fn is_ident<E: AsRef<LispExpr>>(expr: E) -> bool {
    matches!(expr.as_ref(), LispExpr::Ident(_))
}

pub fn is_number<E: AsRef<LispExpr>>(expr: E) -> bool {
    matches!(expr.as_ref(), LispExpr::Number(_))
}