Working on a simple LISP/scheme interpreter.

1 files changed, 71 insertions, 0 deletions

diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..15cf60b
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,71 @@
+#[cfg(test)]
+pub mod tests;
+
+pub mod lib;
+
+use rustyline::error::ReadlineError;
+use rustyline::Editor;
+
+fn read<T: rustyline::Helper>(rl: &mut Editor<T>) -> Option<String> {
+    let readline = rl.readline(">> ");
+    match readline {
+        Ok(line) => {
+            rl.add_history_entry(line.as_str());
+            Some(line)
+        },
+        Err(ReadlineError::Interrupted) => {
+            println!("CTRL-C");
+            None
+        },
+        Err(ReadlineError::Eof) => {
+            println!("CTRL-D");
+            None
+        },
+        Err(err) => {
+            println!("Error: {:?}", err);
+            None
+        }
+    }
+}
+
+fn means_exit(input: &str) -> bool {
+    match input {
+        "exit" | "quit" | ",q" => true,
+        _ => false
+    }
+}
+
+fn eval(env: &mut lib::eval::Env, input: &str) -> String {
+    let sexp = match lib::parse::parse(input) {
+        Ok(x) => x,
+        Err(f) => return f
+    };
+
+    println!("{:?}", sexp);
+    let res = lib::eval::eval(&sexp, env);
+    match res {
+        Ok(x) => format!("{:?}", x),
+        Err(f) => f
+    }
+}
+
+fn main() {
+    let mut env = lib::eval::Env::new();
+    let hist_file = "history.txt";
+
+    // `()` can be used when no completer is required
+    let mut rl = Editor::<()>::new();
+    if rl.load_history(hist_file).is_err() {
+        println!("No previous history.");
+    }
+    loop {
+        let input_line = read(&mut rl);
+        let line = match input_line {
+            None => break,
+            Some(expr) if means_exit(&expr) => break,
+            Some(expr) => expr
+        };
+        println!("{}", eval(&mut env, &line));
+    }
+    rl.save_history(hist_file).unwrap();
+}