Added repl and some documentation. Improved error messages. Removed dead code.

* Removed same_variant in parse::parsetree
* Added SExp::multistep (for use of the repl)

Improved error messages:
* Added parenthesis around types
* Changed how errors propagate inferring generics:
  added the error variant ArgumentsDontMatchGeneric,
  implemented the displaying of it, added tests for
  it.
* Had to change some tests to match for the new changes

1 files changed, 62 insertions, 1 deletions

diff --git a/src/main.rs b/src/main.rs
index e7a11a9..80a4066 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,64 @@
+
+use melisp::parse::parsetree::parse_to_ast;
+use melisp::sexp::{SExp::*, SLeaf::Nil};
+use std::{io, io::Write};
+
 fn main() {
-    println!("Hello, world!");
+    match repl() {
+        Ok(()) => println!("bye :)"),
+        Err(e) => {
+            println!("Error: {}", e);
+            main();
+        },
+    }
 }
+
+fn repl() -> Result<(), String> {
+
+    let stdin = io::stdin();
+    
+    let mut input = String::new();
+
+    let mut stdout = io::stdout();
+    
+    print!("> ");
+    match stdout.flush() {
+        Ok(_) => (),
+        Err(_) => println!("Enter s-expression:"),
+    };
+    let mut success = stdin.read_line(&mut input);
+
+    while success.is_ok() && input != "exit\n" {
+        if let Ok(0) = success {
+            print!("\n");
+            break;
+        }
+
+        let expression = match parse_to_ast(&input) {
+            Ok(SCons(a, b)) if *b == Atom(Nil) => Ok(*a),
+            t => t
+        }?;
+
+        let ty = expression.type_check().map_err(|e| e.to_string())?;
+
+        let result = expression.multistep()?;
+
+        println!("{} : {}", result, ty);
+
+        print!("> ");
+        match stdout.flush() {
+            Ok(_) => (),
+            Err(_) => println!("Enter s-expression:"),
+        };
+        input.clear();
+        success = stdin.read_line(&mut input);
+
+    }
+
+    match success {
+        Ok(_) => Ok(()),
+        Err(e) => Err(format!("read error: {e}")),
+    }
+
+}
+