big progress on rewrite

Signed-off-by: Ava Hahn <ava@aidanis.online>

the_rewrite/src/vars.rs

@@ -0,0 +1,85 @@
+/* relish: versatile lisp shell
+ * Copyright (C) 2021 Aidan Hahn
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+use crate::eval::eval;
+use crate::func::{Args, FTable, Function, Operation};
+use crate::segment::{Seg, Ctr};
+use std::collections::HashMap;
+use std::env;
+/* Mapping between a string token and a tree of Segments
+ * The string token can be found in any Ctr::Symbol value
+ * it is expected that the trees stored are already evaluated
+ */
+pub struct VTable<'a>(HashMap<String, Box<Ctr<'a>>>);
+
+impl<'a> VTable<'a> {
+    // WARNING: make sure var_tree is properly evaluated before storing
+    pub fn insert(&'a mut self, identifier: String, data: Box<Ctr<'a>>) {
+        if let Some(datum) = self.0.insert(identifier, data) {
+            drop(datum);
+        }
+    }
+
+    pub fn get(&'a self, id: String) -> Option<Box<Ctr<'a>>> {
+        return self.0.get(&id);
+    }
+
+    pub fn remove(&self, id: String) {
+        self.0.remove(&id);
+    }
+}
+
+// returns a callback for the stdlib var export function with env_sync on or off
+pub fn get_export<'a> (env_cfg: bool) -> Function<'a> {
+    return Function {
+        name: String::from("export"),
+        loose_syms: true,
+        eval_lazy: true,
+        args: Args::Lazy(2),
+        function: Operation::Internal(Box::new(
+            |ast: &Seg, vars: &mut VTable, funcs: &mut FTable| -> Ctr {
+                if let Ctr::Symbol(identifier) = *ast.car {
+                    match *ast.cdr {
+                        Ctr::Seg(ref data_tree) => match eval(&Box::new(data_tree), vars, funcs, false) {
+                            Ok(seg) => match *seg {
+                                Ctr::Seg(val) => {
+                                    vars.insert(identifier, val.car);
+                                    if env_cfg {
+                                        env::set_var(identifier, val.car.to_string())
+                                    }
+                                },
+                                _ =>  eprintln!("impossible args to export"),
+                            },
+                            Err(e) =>  eprintln!("couldnt eval symbol: {}", e),
+                        },
+                        Ctr::None => {
+                            vars.remove(identifier);
+                            if env_cfg {
+                                env::remove_var(identifier);
+                            }
+                        },
+                        _ =>  eprintln!("args not in standard form"),
+                    }
+                } else {
+                    eprintln!("first argument to export must be a symbol");
+                }
+                return Ctr::None;
+            },
+        )),
+    };
+}
+