68 lines
2.0 KiB
Rust
68 lines
2.0 KiB
Rust
/** Serene --- Yet an other Lisp
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*
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* Copyright (c) 2020 Sameer Rahmani <lxsameer@gnu.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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use crate::ast::Expr;
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use std::collections::HashMap;
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/// This struct describes the values in the scope.
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pub struct ScopeElement {
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element_type: Expr,
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public: bool,
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}
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/// Scopes in **Serene** are simply represented by hashmaps. Each
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/// Scope optionally has a parent scope that lookups fallback to
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/// if the lookup key is missing from the current scope.
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pub struct Scope {
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parent: Option<Box<Scope>>,
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symbol_table: HashMap<String, ScopeElement>,
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}
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impl Scope {
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pub fn new(_parent: Option<Scope>) -> Scope {
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let p = match _parent {
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Some(x) => Some(Box::new(x)),
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None => None,
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};
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Scope {
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parent: p,
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symbol_table: HashMap::new(),
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}
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}
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/// Lookup the given `key` in the scope and if it is not in the current
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/// scope look it up in the `parent` scope.
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pub fn lookup(&self, key: &str) -> Option<&ScopeElement> {
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if self.symbol_table.contains_key(key) {
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self.symbol_table.get(key)
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} else {
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match &self.parent {
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Some(x) => x.lookup(key),
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None => None,
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}
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}
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}
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pub fn insert(&mut self, key: &str, val: Expr, public: bool) {
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let v = ScopeElement {
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public,
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element_type: val,
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};
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self.symbol_table.insert(key.to_string(), v);
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}
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}
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