From dbcaa0df655bdd11c6d01ce28e018fc1e80ed394 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Tue, 30 Mar 2021 16:52:15 +0530
Subject: better parse errors; include lisp stdlib

---
 src/lisp/error.rs   |  25 ++++++++++---
 src/lisp/eval.rs    |  52 ++++++++++++++++----------
 src/lisp/expr.rs    |  60 ++++++++++++++++++++++++++----
 src/lisp/lex.rs     |  22 +++++++----
 src/lisp/prelude.rs | 104 +++++++++++++++++++++++++++++++++++++++++++++-------
 src/lisp/std.lisp   |  26 +++++++++++++
 6 files changed, 235 insertions(+), 54 deletions(-)
 create mode 100644 src/lisp/std.lisp

diff --git a/src/lisp/error.rs b/src/lisp/error.rs
index 6d28c22..53681d8 100644
--- a/src/lisp/error.rs
+++ b/src/lisp/error.rs
@@ -3,19 +3,23 @@ use crate::lisp::{
     lex::{Span, SpanDisplay},
 };
 
-use std::fmt;
+use std::{fmt, io};
 
-#[derive(Debug, PartialEq, Clone)]
+#[derive(Debug)]
 pub enum LispError {
     Parse(ParseError),
     Eval(EvalError),
+    Stringified(String),
 }
 
+impl std::error::Error for LispError {}
+
 impl fmt::Display for LispError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Parse(p) => write!(f, "parse error: {}", p.kind),
             Self::Eval(e) => write!(f, "eval error: {}", e),
+            Self::Stringified(s) => write!(f, "{}", s),
         }
     }
 }
@@ -30,9 +34,12 @@ impl ParseError {
     pub fn new(span: Span, kind: ParseErrorKind) -> Self {
         Self { span, kind }
     }
-    pub fn display(&self, text: &str) -> String {
-        let SpanDisplay { line, col, .. } = SpanDisplay::highlight_span(self.span, text);
-        format!("line {}, col {}: {}", line, col, self.kind)
+    pub fn display(&self, text: &str, file_name: &str) -> String {
+        let SpanDisplay { line, col, .. } = SpanDisplay::highlight_span(self.span, text, file_name);
+        format!(
+            "in file `{}`; line {}, col {}: {}",
+            file_name, line, col, self.kind
+        )
     }
 }
 
@@ -82,7 +89,7 @@ impl From<ParseError> for LispError {
     }
 }
 
-#[derive(Debug, PartialEq, Clone)]
+#[derive(Debug)]
 pub enum EvalError {
     ArgumentCount(Arity),
     BadForm,
@@ -90,7 +97,10 @@ pub enum EvalError {
     DivByZero,
     TypeMismatch,
     NoFileName,
+    AccessEmptyList,
+    ScriptLoadError(io::Error),
     CustomInternal(&'static str),
+    Custom(String),
 }
 
 impl fmt::Display for EvalError {
@@ -113,7 +123,10 @@ impl fmt::Display for EvalError {
             Self::TypeMismatch => write!(f, "mismatched types"),
             Self::DivByZero => write!(f, "attempt to divide by zero"),
             Self::NoFileName => write!(f, "no file name specified"),
+            Self::AccessEmptyList => write!(f, "attempted to access empty list"),
+            Self::ScriptLoadError(s) => write!(f, "error while loading script: {}", s),
             Self::CustomInternal(s) => write!(f, "{}", s),
+            Self::Custom(s) => write!(f, "error: {}", s),
         }
     }
 }
diff --git a/src/lisp/eval.rs b/src/lisp/eval.rs
index 3a3a61e..44540c0 100644
--- a/src/lisp/eval.rs
+++ b/src/lisp/eval.rs
@@ -6,6 +6,7 @@ use crate::{
         number::LispNumber,
         Environment,
     },
+    type_match,
 };
 
 use std::convert::TryInto;
@@ -20,7 +21,14 @@ pub fn eval(expr: &LispExpr, app: &mut AppState) -> Result<LispExpr, LispError>
         LispExpr::Number(_) => Ok(expr.clone()),
         LispExpr::BoolLit(_) => Ok(expr.clone()),
         LispExpr::Ident(ref id) => lookup_extended(&app.lisp_env, id),
-        LispExpr::Quote(_, _) => Ok(expr.clone()),
+        LispExpr::Quote(item, _) => match item.as_ref() {
+            i @ LispExpr::Unit
+            | i @ LispExpr::StringLit(_)
+            | i @ LispExpr::Char(_)
+            | i @ LispExpr::Number(_)
+            | i @ LispExpr::BoolLit(_) => Ok(i.clone()),
+            _ => Ok(*item.clone()),
+        },
         LispExpr::List(li) => {
             let func_expr = &li[0];
             match func_expr {
@@ -29,6 +37,7 @@ pub fn eval(expr: &LispExpr, app: &mut AppState) -> Result<LispExpr, LispError>
                     "set!" => set_var(&li[1..], app),
                     "lambda" => create_lambda(&li[1..]),
                     "if" => eval_if(&li[1..], app),
+                    "quote" => eval_quote(&li[1..]),
                     _ => {
                         let mut new_ls = vec![eval(&func_expr, app)?];
                         new_ls.extend(li[1..].to_vec());
@@ -99,7 +108,7 @@ pub fn define_var(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, Lis
         [LispExpr::List(shorthand), LispExpr::List(body)] => {
             // (define (func arg) <body>) shorthand
 
-            let id = unwrap_ident(shorthand[0].clone());
+            let id = shorthand[0].unwrap_ident();
             let params = if shorthand.len() > 1 {
                 &shorthand[1..]
             } else {
@@ -163,13 +172,12 @@ pub fn create_lambda(cdr: &[LispExpr]) -> Result<LispExpr, LispError> {
     }
     info!("creating lambda");
     match cdr {
-        [LispExpr::List(params), LispExpr::List(body)]
-            if params.iter().all(|p| matches!(p, LispExpr::Ident(_))) =>
+        [LispExpr::List(params), LispExpr::List(body)] if type_match!(params, (..) => LispExpr::Ident(_)) =>
         {
             return Ok(LispExpr::Function(LispFunction {
                 params: params
                     .into_iter()
-                    .map(|p| unwrap_ident(p.clone()))
+                    .map(|p| p.unwrap_ident())
                     .collect::<Vec<_>>(),
                 body: body.clone(),
             }));
@@ -202,6 +210,26 @@ pub fn eval_if(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispEr
     }
 }
 
+pub fn eval_quote(args: &[LispExpr]) -> Result<LispExpr, LispError> {
+    let arity = Arity::Exact(1);
+    if !arity.is_valid(args) {
+        return Err(arity.to_error());
+    } else {
+        match &args[0] {
+            LispExpr::Quote(item, depth) => Ok(LispExpr::Quote(item.clone(), depth + 1)),
+            i @ LispExpr::Unit
+            | i @ LispExpr::StringLit(_)
+            | i @ LispExpr::Char(_)
+            | i @ LispExpr::Number(_)
+            | i @ LispExpr::BoolLit(_) => Ok(i.clone()),
+            _ => {
+                let quoted_expr = Box::new(args[0].clone());
+                Ok(LispExpr::Quote(quoted_expr, 1))
+            }
+        }
+    }
+}
+
 pub fn lookup_extended(env_list: &[Environment], key: &str) -> Result<LispExpr, LispError> {
     if env_list.is_empty() {
         return Err(EvalError::UnboundVariable(key.into()).into());
@@ -215,20 +243,6 @@ pub fn lookup_extended(env_list: &[Environment], key: &str) -> Result<LispExpr,
     }
 }
 
-pub fn unwrap_number(n: &LispExpr) -> &LispNumber {
-    match n {
-        LispExpr::Number(i) => i,
-        _ => panic!("unwrap_number expected number"),
-    }
-}
-
-pub fn unwrap_ident(i: LispExpr) -> String {
-    match i {
-        LispExpr::Ident(i) => i,
-        _ => panic!("unwrap_ident expected string"),
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/lisp/expr.rs b/src/lisp/expr.rs
index 934bb4a..9f2dc8d 100644
--- a/src/lisp/expr.rs
+++ b/src/lisp/expr.rs
@@ -117,6 +117,8 @@ impl LispExpr {
                 .iter()
                 .zip(o)
                 .all(|(a, b)| matches!(a.compare(b, envs), Ok(true)))),
+            (LispExpr::List(s), LispExpr::Unit) => Ok(s.len() == 0),
+            (LispExpr::Unit, LispExpr::List(s)) => Ok(s.len() == 0),
             (LispExpr::StringLit(s), LispExpr::StringLit(o)) => Ok(s == o),
             (LispExpr::Char(s), LispExpr::Char(o)) => Ok(s == o),
             (LispExpr::BoolLit(s), LispExpr::BoolLit(o)) => Ok(s == o),
@@ -142,6 +144,56 @@ impl LispExpr {
             _ => Err(EvalError::TypeMismatch.into()),
         }
     }
+
+    // have these be code gen'd somehow
+    pub fn unwrap_number(&self) -> LispNumber {
+        match &self {
+            LispExpr::Number(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_number` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_list(&self) -> Vec<LispExpr> {
+        match &self {
+            LispExpr::List(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_number` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_stringlit(&self) -> String {
+        match &self {
+            LispExpr::StringLit(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_stringlit` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_ident(&self) -> String {
+        match &self {
+            LispExpr::Ident(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_ident` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_primitive_func(&self) -> PrimitiveFunc {
+        match &self {
+            LispExpr::PrimitiveFunc(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_primitive_func` on invalid type"),
+        }
+    }
+
+    pub fn unwrap_function(&self) -> LispFunction {
+        match &self {
+            LispExpr::Function(p) => p.clone(),
+            _ => panic!("attempt to call `unwrap_function` on invalid type"),
+        }
+    }
+
+    pub fn cast_bool(&self) -> bool {
+        match &self {
+            LispExpr::BoolLit(false) => false,
+            _ => true,
+        }
+    }
 }
 
 impl fmt::Display for LispExpr {
@@ -270,11 +322,3 @@ impl TryFrom<LispExpr> for BoolLit {
         }
     }
 }
-
-pub fn is_ident<E: AsRef<LispExpr>>(expr: E) -> bool {
-    matches!(expr.as_ref(), LispExpr::Ident(_))
-}
-
-pub fn is_number<E: AsRef<LispExpr>>(expr: E) -> bool {
-    matches!(expr.as_ref(), LispExpr::Number(_))
-}
diff --git a/src/lisp/lex.rs b/src/lisp/lex.rs
index e514d7f..5d3030b 100644
--- a/src/lisp/lex.rs
+++ b/src/lisp/lex.rs
@@ -1,6 +1,6 @@
 use std::{fmt, str::CharIndices};
 
-use crate::lisp::error::{LispError, ParseError, ParseErrorKind};
+use crate::lisp::error::{ParseError, ParseErrorKind};
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub enum Token<'a> {
@@ -75,21 +75,27 @@ impl Span {
 }
 
 #[derive(Debug, Clone)]
-pub struct SpanDisplay<'src> {
+pub struct SpanDisplay<'src, 'file> {
+    pub file_name: &'file str,
     pub source: &'src str,
     pub line: usize,
     pub col: usize,
 }
 
-impl<'src> SpanDisplay<'src> {
-    pub fn highlight_span(span: Span, source: &'src str) -> Self {
+impl<'src, 'file> SpanDisplay<'src, 'file> {
+    pub fn highlight_span(span: Span, source: &'src str, file_name: &'file str) -> Self {
         let line_start = match source[..span.low as usize].rfind('\n') {
             Some(pos) => pos + 1,
             None => 0,
         };
         let line = source[..line_start].chars().filter(|&c| c == '\n').count() + 1;
         let col = source[line_start..span.low as usize].chars().count();
-        Self { source, line, col }
+        Self {
+            file_name,
+            source,
+            line,
+            col,
+        }
     }
 }
 
@@ -108,7 +114,7 @@ impl<'a> Lexer<'a> {
         }
     }
 
-    pub fn next_token(&mut self) -> Result<(Span, Token<'a>), LispError> {
+    pub fn next_token(&mut self) -> Result<(Span, Token<'a>), ParseError> {
         let mut chars = self.input.char_indices();
 
         while let Some((ind, chr)) = chars.next() {
@@ -142,13 +148,13 @@ impl<'a> Lexer<'a> {
             let (size, token) = match res {
                 Ok(v) => v,
                 Err(kind) => {
-                    return Err(LispError::Parse(ParseError {
+                    return Err(ParseError {
                         span: Span {
                             low,
                             high: low + chr.len_utf8() as u32,
                         },
                         kind,
-                    }))
+                    })
                 }
             };
             self.cur_pos += size as u32;
diff --git a/src/lisp/prelude.rs b/src/lisp/prelude.rs
index d8a930b..dffd9f4 100644
--- a/src/lisp/prelude.rs
+++ b/src/lisp/prelude.rs
@@ -3,11 +3,12 @@ use crate::{
     lisp::{
         error::{EvalError, LispError},
         eval::eval,
-        expr::{is_ident, Arity, LispExpr},
+        expr::{Arity, LispExpr},
         number::LispNumber,
         Environment,
     },
     primitive,
+    utils::load_script,
 };
 
 use std::{convert::TryInto, fs::File, io::Write};
@@ -27,7 +28,7 @@ macro_rules! primitive {
 
 #[macro_export]
 macro_rules! type_match {
-    ($args:expr, $($range:expr => $kind:pat),+) => {
+    ($args:expr, $($range:literal => $kind:pat),+) => {
         {
             let mut temp_vec = vec![];
             $(
@@ -35,10 +36,21 @@ macro_rules! type_match {
             )+
             temp_vec.iter().all(|&t| t)
         }
+    };
+    ($args:expr, $($range:expr => $kind:pat),+) => {
+        {
+            let mut temp_vec = vec![];
+            $(
+                for arg in &$args[$range] {
+                    temp_vec.push(matches!(arg, $kind));
+                }
+            )+
+            temp_vec.iter().all(|&t| t)
+        }
     }
 }
 
-pub fn new_env() -> Environment {
+pub fn new_env() -> Result<Environment, LispError> {
     let mut env = Environment::new();
 
     primitive!(env, Arity::Atleast(2), "+", |args, _| {
@@ -113,7 +125,7 @@ pub fn new_env() -> Environment {
     });
 
     primitive!(env, Arity::Exact(1), "not", |args, _| {
-        if matches!(&args[0], LispExpr::BoolLit(false)) {
+        if type_match!(args, 0 => LispExpr::BoolLit(false)) {
             Ok(LispExpr::BoolLit(true))
         } else {
             Ok(LispExpr::BoolLit(false))
@@ -121,11 +133,7 @@ pub fn new_env() -> Environment {
     });
 
     primitive!(env, Arity::Atleast(1), "begin", |args, _| {
-        if args.is_empty() {
-            Err(EvalError::ArgumentCount(Arity::Atleast(1)).into())
-        } else {
-            Ok(args.into_iter().last().unwrap().clone())
-        }
+        Ok(args.into_iter().last().unwrap().clone())
     });
 
     primitive!(env, Arity::Exact(0), "quit", |_, app| {
@@ -136,7 +144,7 @@ pub fn new_env() -> Environment {
     primitive!(env, Arity::Exact(2), "eq?", |args, app| {
         let s = &args[0];
         let o = &args[1];
-        info!("comparing {} {}", s, o);
+        info!("comparing s: {} and o: {}", s, o);
         let result = s.compare(o, &app.lisp_env);
         result.map(LispExpr::BoolLit)
     });
@@ -188,7 +196,7 @@ pub fn new_env() -> Environment {
     primitive!(env, Arity::Exact(1), "string-len", |args, _| {
         if type_match!(args, 0 => LispExpr::StringLit(_)) {
             Ok(LispExpr::Number(LispNumber::Integer(
-                args[0].as_ref().len() as i64,
+                args[0].unwrap_stringlit().len() as i64,
             )))
         } else {
             Err(EvalError::TypeMismatch.into())
@@ -218,7 +226,7 @@ pub fn new_env() -> Environment {
             0
         };
         if let [LispExpr::Quote(kind, _)] = args {
-            if is_ident(kind) {
+            if matches!(kind.as_ref(), LispExpr::Ident(_)) {
                 match (&**kind).as_ref() {
                     "fill" => app.brush = Brush::Fill,
                     "circle" => app.brush = Brush::new(old_size),
@@ -250,9 +258,79 @@ pub fn new_env() -> Environment {
         }
     });
 
+    primitive!(env, Arity::Exact(2), "filter", |args, app| {
+        let mut apply_filter =
+            |func: &LispExpr, ls: &Vec<LispExpr>| -> Result<Vec<LispExpr>, LispError> {
+                let mut result = vec![];
+                for arg in ls.into_iter() {
+                    if eval(&LispExpr::List(vec![func.clone(), arg.clone()]), app)?.cast_bool() {
+                        result.push(arg.clone())
+                    }
+                }
+                Ok(result)
+            };
+        if matches!(&args[0], LispExpr::Function(_) | LispExpr::PrimitiveFunc(_)) {
+            match &args[1] {
+                LispExpr::List(ls) => return Ok(LispExpr::List(apply_filter(&args[0], ls)?)),
+                _ => return Err(EvalError::TypeMismatch.into()),
+            }
+        } else {
+            return Err(EvalError::TypeMismatch.into());
+        }
+    });
+
+    primitive!(env, Arity::Exact(1), "car", |args, _| {
+        if type_match!(args, 0 => LispExpr::List(_)) {
+            return Ok(args[0].unwrap_list().swap_remove(0));
+        } else if type_match!(args, 0 => LispExpr::Unit) {
+            return Err(EvalError::AccessEmptyList.into());
+        } else {
+            return Err(EvalError::TypeMismatch.into());
+        }
+    });
+
+    primitive!(env, Arity::Exact(1), "cdr", |args, _| {
+        if type_match!(args, 0 => LispExpr::List(_)) {
+            let mut ls = args[0].unwrap_list();
+            if ls.len() == 0 {
+                return Err(EvalError::AccessEmptyList.into());
+            } else if ls.len() == 1 {
+                return Ok(LispExpr::Unit);
+            } else {
+                ls.remove(0);
+                return Ok(LispExpr::List(ls));
+            }
+        } else if type_match!(args, 0 => LispExpr::Unit) {
+            return Err(EvalError::AccessEmptyList.into());
+        } else {
+            return Err(EvalError::TypeMismatch.into());
+        }
+    });
+
     primitive!(env, Arity::Atleast(1), "list", |args, _| {
         return Ok(LispExpr::List(args.to_vec()));
     });
 
-    env
+    primitive!(env, Arity::Exact(1), "load-script", |args, app| {
+        if type_match!(args, 0 => LispExpr::StringLit(_)) {
+            let path = args[0].unwrap_stringlit();
+            load_script(&path, app).map(|_| LispExpr::Unit)
+        } else {
+            return Err(EvalError::TypeMismatch.into());
+        }
+    });
+
+    primitive!(env, Arity::Atleast(1), "error", |args, _| {
+        if type_match!(args, 0 => LispExpr::StringLit(_)) {
+            let mut s = String::from(args[0].unwrap_stringlit());
+            for arg in args.into_iter().skip(1) {
+                s.push_str(&format!(" {}", arg));
+            }
+            return Err(EvalError::Custom(s).into());
+        } else {
+            return Err(EvalError::TypeMismatch.into());
+        }
+    });
+
+    Ok(env)
 }
diff --git a/src/lisp/std.lisp b/src/lisp/std.lisp
new file mode 100644
index 0000000..c723a13
--- /dev/null
+++ b/src/lisp/std.lisp
@@ -0,0 +1,26 @@
+(define (caar ls) (car (car ls)))
+(define (caaar ls) (car (caar ls)))
+(define (caaaar ls) (car (caaar ls)))
+(define (caaaaar ls) (car (caaaar ls)))
+
+(define (cddr ls) (cdr (cdr ls)))
+(define (cdddr ls) (cdr (cddr ls)))
+(define (cddddr ls) (cdr (cdddr ls)))
+(define (cdddddr ls) (cdr (cddddr ls)))
+
+(define (null? ls) (eq? ls '()))
+
+(define (length ls)
+  (if (null? ls)
+    0
+    (+ 1 (length (cdr ls)))))
+
+(define (fold init accumulator ls)
+  (if (null? ls)
+    init
+    (fold (accumulator init (car ls))
+          accumulator
+          (cdr ls))))
+
+(define (sum ls) (fold 0 + ls))
+(define (product ls) (fold 1 * ls))
-- 
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