Eval cycle implemented

Yet to be implement:
- Environment
- Function calls

Signed-off-by: teo3300 <matteo.rogora@live.it>

src/mal_core.rs

@@ -0,0 +1,51 @@
+use crate::envs::Env;
+use crate::types::MalType::*;
+use crate::types::{MalRet, MalType};
+
+fn function_call(list: MalType) -> MalRet {
+    match list {
+        List(list) => {
+            let _func = &list[0];
+            if list.len() > 1 {
+                let _ast = &list[1..list.len() - 1];
+                todo!("call: func(args)");
+            } else {
+                todo!("call: func()");
+            }
+        }
+        _ => Err("YOU SHOULD NOT BE HERE".to_string()),
+    }
+}
+
+pub fn eval(ast: MalType, env: &Env) -> MalRet {
+    match &ast {
+        List(list) => {
+            if list.is_empty() {
+                Ok(ast)
+            } else {
+                let ev = eval_ast(ast, env)?;
+                function_call(ev)
+            }
+        }
+        _ => eval_ast(ast, env),
+    }
+}
+
+fn eval_list(list: Vec<MalType>, env: &Env) -> MalRet {
+    let mut ret = Vec::new();
+    for el in list {
+        match eval(el, env) {
+            Ok(val) => ret.push(val),
+            Err(err) => return Err(err),
+        }
+    }
+    Ok(List(ret))
+}
+
+pub fn eval_ast(ast: MalType, env: &Env) -> MalRet {
+    match ast {
+        Sym(sym) => env.solve(sym), // resolve
+        List(list) => eval_list(list, env),
+        _ => Ok(ast), // Default behavior, do not resolve
+    }
+}