object/
builtins.rs

1use crate::{BuiltinFunc, Object};
2use std::rc::Rc;
3
4#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
5pub enum BuiltinId {
6    Len,
7    Puts,
8    First,
9    Last,
10    Rest,
11    Push,
12}
13
14#[derive(Clone, Copy)]
15pub struct BuiltinDefinition {
16    pub name: &'static str,
17    pub id: BuiltinId,
18    pub function: BuiltinFunc,
19}
20
21lazy_static! {
22    pub static ref BuiltIns: Vec<BuiltinDefinition> = vec![
23        BuiltinDefinition {
24            name: "len",
25            id: BuiltinId::Len,
26            function: len
27        },
28        BuiltinDefinition {
29            name: "puts",
30            id: BuiltinId::Puts,
31            function: puts
32        },
33        BuiltinDefinition {
34            name: "first",
35            id: BuiltinId::First,
36            function: first
37        },
38        BuiltinDefinition {
39            name: "last",
40            id: BuiltinId::Last,
41            function: last
42        },
43        BuiltinDefinition {
44            name: "rest",
45            id: BuiltinId::Rest,
46            function: rest
47        },
48        BuiltinDefinition {
49            name: "push",
50            id: BuiltinId::Push,
51            function: push
52        },
53        BuiltinDefinition {
54            name: "print",
55            id: BuiltinId::Puts,
56            function: puts
57        },
58    ];
59}
60
61// a failed try
62// rust sucks: https://stackoverflow.com/a/27896014/1713757
63// pub static BUILTINS: HashMap<String, BuiltinFunc> = vec![(String::from("len"), len as BuiltinFunc) ]
64//     .into_iter()
65//     .collect();
66
67/// Reject a call whose argument count does not match the builtin's arity,
68/// mirroring the checks the gc runtime performs in `gc/value.rs`. Returns the
69/// `Object::Error` the builtin should hand back, or `None` when the call is
70/// well-formed. Every fixed-arity builtin must call this before touching
71/// `args[..]`, otherwise a short call indexes out of bounds and panics.
72fn check_arity(name: &str, args: &[Rc<Object>], expected: usize) -> Option<Rc<Object>> {
73    if args.len() == expected {
74        return None;
75    }
76    Some(Rc::from(Object::Error(format!(
77        "builtin {} expected {} argument{}, got {}",
78        name,
79        expected,
80        if expected == 1 { "" } else { "s" },
81        args.len()
82    ))))
83}
84
85pub fn len(args: Vec<Rc<Object>>) -> Rc<Object> {
86    if let Some(error) = check_arity("len", &args, 1) {
87        return error;
88    }
89    Rc::from(match &*args[0] {
90        Object::String(s) => Object::Integer(s.len() as i64),
91        Object::Array(a) => Object::Integer(a.len() as i64),
92        o => Object::Error(format!("builtin len not supported for for type {}", o)),
93    })
94}
95
96pub fn puts(args: Vec<Rc<Object>>) -> Rc<Object> {
97    args.iter().for_each(|obj| println!("{}", obj));
98    Rc::from(Object::Null)
99}
100
101pub fn first(args: Vec<Rc<Object>>) -> Rc<Object> {
102    if let Some(error) = check_arity("first", &args, 1) {
103        return error;
104    }
105    match &*args[0] {
106        Object::Array(s) => match s.first() {
107            Some(obj) => Rc::clone(obj),
108            None => Rc::new(Object::Null),
109        },
110        o => Rc::new(Object::Error(format!("builtin first not supported for for type {}", o))),
111    }
112}
113
114pub fn last(args: Vec<Rc<Object>>) -> Rc<Object> {
115    if let Some(error) = check_arity("last", &args, 1) {
116        return error;
117    }
118    match &*args[0] {
119        Object::Array(s) => match s.last() {
120            Some(obj) => Rc::clone(obj),
121            None => Rc::new(Object::Null),
122        },
123        o => Rc::new(Object::Error(format!("builtin last not supported for for type {}", o))),
124    }
125}
126
127pub fn rest(args: Vec<Rc<Object>>) -> Rc<Object> {
128    if let Some(error) = check_arity("rest", &args, 1) {
129        return error;
130    }
131    match &*args[0] {
132        Object::Array(s) => {
133            let len = s.len();
134            if len > 0 {
135                let new_array = s[1..len].to_vec();
136                return Rc::new(Object::Array(new_array));
137            }
138            return Rc::new(Object::Null);
139        }
140        o => Rc::new(Object::Error(format!("builtin rest not supported for for type {}", o))),
141    }
142}
143
144pub fn push(args: Vec<Rc<Object>>) -> Rc<Object> {
145    if let Some(error) = check_arity("push", &args, 2) {
146        return error;
147    }
148    match &*args[0] {
149        Object::Array(s) => {
150            let mut new_array = s.clone();
151            new_array.push(Rc::clone(&args[1]));
152            return Rc::new(Object::Array(new_array));
153        }
154        o => Rc::new(Object::Error(format!("builtin push not supported for for type {}", o))),
155    }
156}
object/builtins.rs

object/
builtins.rs
