val 0.4.2

An arbitrary precision calculator language
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 super::*;

#[derive(Clone, Default)]
pub struct Environment {
  pub(crate) config: Config,
  pub(crate) frame: Rc<RefCell<Frame>>,
}

impl Environment {
  pub fn add_function(&self, name: &str, function: Function) {
    let mut frame = self.frame.borrow_mut();

    frame.symbols.entry(name.to_owned()).or_default().function = Some(function);
  }

  pub fn add_symbol(&self, name: &str, value: Value) {
    let mut frame = self.frame.borrow_mut();

    frame.symbols.entry(name.to_owned()).or_default().value = Some(value);
  }

  fn assign_existing_symbol(
    &self,
    name: &str,
    value: Value,
  ) -> std::result::Result<(), Value> {
    let parent = {
      let mut frame = self.frame.borrow_mut();

      match frame.symbols.get_mut(name) {
        Some(symbol) if symbol.value.is_some() => {
          symbol.value = Some(value);
          return Ok(());
        }
        _ => frame.parent.clone(),
      }
    };

    match parent {
      Some(parent) => parent.assign_existing_symbol(name, value),
      None => Err(value),
    }
  }

  pub(crate) fn assign_symbol(&self, name: &str, value: Value) {
    if let Err(value) = self.assign_existing_symbol(name, value) {
      self.add_symbol(name, value);
    }
  }

  pub(crate) fn function(
    &self,
    name: &str,
    span: Span,
  ) -> Result<Function, Error> {
    match self.resolve_function(name) {
      Some(function) => Ok(function),
      None if self.resolve_symbol(name).is_some() => {
        Err(Error::new(span, format!("`{name}` is not a function")))
      }
      None => Err(Error::new(
        span,
        format!("Function `{name}` is not defined"),
      )),
    }
  }

  fn local_function(&self, name: &str) -> Option<Function> {
    let frame = self.frame.borrow();

    let symbol = frame.symbols.get(name)?;

    symbol.function.clone().or_else(|| match &symbol.value {
      Some(Value::Function(function)) => Some(function.clone()),
      _ => None,
    })
  }

  fn local_symbol(&self, name: &str) -> Option<Value> {
    let frame = self.frame.borrow();

    let symbol = frame.symbols.get(name)?;

    symbol
      .value
      .clone()
      .or_else(|| symbol.function.clone().map(Value::Function))
  }

  #[must_use]
  pub fn new(config: Config) -> Self {
    let environment = Self {
      config,
      frame: Rc::new(RefCell::new(Frame::default())),
    };

    for builtin in inventory::iter::<&dyn Builtin> {
      for name in once(builtin.name()).chain(builtin.aliases().iter().copied())
      {
        match builtin.value(config) {
          Value::Function(Function::Builtin {
            arity, function, ..
          }) => {
            environment.add_function(
              name,
              Function::Builtin {
                arity,
                function,
                name,
              },
            );
          }
          Value::Function(function) => {
            environment.add_function(name, function);
          }
          value => {
            environment.add_symbol(name, value);
          }
        }
      }
    }

    environment
  }

  fn resolve_function(&self, name: &str) -> Option<Function> {
    self
      .local_function(name)
      .or_else(|| self.frame.borrow().parent.clone()?.resolve_function(name))
  }

  pub(crate) fn resolve_symbol(&self, name: &str) -> Option<Value> {
    self
      .local_symbol(name)
      .or_else(|| self.frame.borrow().parent.clone()?.resolve_symbol(name))
  }

  pub(crate) fn with_parent(parent: Environment) -> Self {
    Self {
      config: parent.config,
      frame: Rc::new(RefCell::new(Frame {
        parent: Some(parent),
        symbols: HashMap::new(),
      })),
    }
  }
}

impl fmt::Debug for Environment {
  fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
    f.debug_struct("Environment")
      .field("config", &self.config)
      .finish_non_exhaustive()
  }
}