keep working on some things

src/main.rs

@@ -43,7 +43,7 @@ mod vm;
 use crate::vm::*;
 
 pub fn main() {
-    let src = "[1, 2, 3]";
+    let src = "let (x, 2) = (1, 2); x";
     let (tokens, lex_errs) = lexer().parse(src).into_output_errors();
     if lex_errs.len() > 0 {
         println!("{:?}", lex_errs);

src/parser.rs

@@ -197,6 +197,8 @@ where
         Token::Boolean(b) => Pattern::Boolean(b),
         Token::Number(n) => Pattern::Number(n),
         Token::Keyword(k) => Pattern::Keyword(k),
+        // todo: actual string patterns
+        Token::String(s) => Pattern::String(s)
     }
     .map_with(|a, e| (a, e.span()));
 

src/vm.rs

@@ -5,7 +5,7 @@ use std::rc::Rc;
 
 #[derive(Clone, Debug)]
 pub struct LudusError {
-    msg: String,
+    msg: &'static str,
 }
 
 // oy
@@ -19,6 +19,8 @@ pub struct LudusError {
 // to work with a mutable borrow of ctx
 pub struct Ctx<'src> {
     pub locals: Vec<(&'src str, Value<'src>)>,
+    // pub names: Vec<&'src str>,
+    // pub values: Vec<Value<'src>>,
 }
 
 impl<'src> Ctx<'src> {
@@ -35,6 +37,70 @@ impl<'src> Ctx<'src> {
     }
 }
 
+pub fn match_eq<T, U>(x: T, y: T, z: U) -> Option<U>
+where
+    T: PartialEq,
+{
+    if x == y {
+        Some(z)
+    } else {
+        None
+    }
+}
+
+pub fn matchh<'src, 'a>(
+    patt: &Pattern<'src>,
+    val: &Value<'src>,
+    ctx: &'a mut Vec<(&'src str, Value<'src>)>,
+) -> Option<&'a mut Vec<(&'src str, Value<'src>)>> {
+    match (patt, val) {
+        (Pattern::Nil, Value::Nil) => Some(ctx),
+        (Pattern::Placeholder, _) => Some(ctx),
+        (Pattern::Number(x), Value::Number(y)) => match_eq(x, y, ctx),
+        (Pattern::Boolean(x), Value::Boolean(y)) => match_eq(x, y, ctx),
+        (Pattern::Keyword(x), Value::Keyword(y)) => match_eq(x, y, ctx),
+        (Pattern::String(x), Value::String(y)) => match_eq(x, y, ctx),
+        (Pattern::Word(w), val) => {
+            ctx.push((w, val.clone()));
+            Some(ctx)
+        }
+        // todo: add splats to these match clauses
+        (Pattern::Tuple(x), Value::Tuple(y)) => {
+            if x.len() != y.len() {
+                return None;
+            };
+            let to = ctx.len();
+            for i in 0..x.len() {
+                if let None = matchh(&x[i].0, &y[i], ctx) {
+                    while ctx.len() > to {
+                        ctx.pop();
+                    }
+                    return None;
+                }
+            }
+            Some(ctx)
+        }
+        (Pattern::List(x), Value::List(y)) => {
+            if x.len() != y.len() {
+                return None;
+            };
+            let to = ctx.len();
+            for i in 0..x.len() {
+                if let None = matchh(&x[i].0, y.get(i).unwrap(), ctx) {
+                    while ctx.len() > to {
+                        ctx.pop();
+                    }
+                    return None;
+                }
+            }
+            Some(ctx)
+        }
+        (Pattern::Pair(_, _), _) => todo!("dictionary patterns still to do"),
+        (Pattern::Dict(_), _) => todo!("dictionary patterns still to do"),
+        _ => None,
+    }
+}
+
 pub fn eval<'src, 'a>(
     ast: &Ast<'src>,
     ctx: &'a mut Vec<(&'src str, Value<'src>)>,
@@ -46,10 +112,14 @@ pub fn eval<'src, 'a>(
         Ast::Keyword(k) => Ok(Value::Keyword(k)),
         Ast::String(s) => Ok(Value::String(s)),
         Ast::Block(exprs) => {
+            let to = ctx.len();
             let mut result = Value::Nil;
             for (expr, _) in exprs {
                 result = eval(expr, ctx)?;
             }
+            while ctx.len() > to {
+                ctx.pop();
+            }
             Ok(result)
         }
         Ast::If(cond, if_true, if_false) => {
@@ -82,6 +152,13 @@ pub fn eval<'src, 'a>(
             };
             Ok(val)
         }
+        Ast::Let(patt, expr) => {
+            let val = eval(&expr.0, ctx)?;
+            match matchh(&patt.0, &val, ctx) {
+                Some(_) => Ok(val),
+                None => Err(LudusError { msg: "No match" }),
+            }
+        }
         _ => todo!(),
     }
 }