From d0840759b3a54a8163b6f43bc9d980773ae8fe77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20R=C3=B6ger?= <jonas.roeger@tu-dortmund.de>
Date: Tue, 31 Mar 2026 20:14:49 +0200
Subject: [PATCH] feat(core): Display for EvalError + ParserError

---
 lispers-core/src/lisp/eval.rs        |  6 +++++-
 lispers-core/src/parser/parser.rs    | 11 +++++++++++
 lispers-core/src/parser/token.rs     | 19 +++++++++++++++++++
 lispers-core/src/parser/tokenizer.rs | 10 ++++++++++
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/lispers-core/src/lisp/eval.rs b/lispers-core/src/lisp/eval.rs
index a122849..1d89f8e 100644
--- a/lispers-core/src/lisp/eval.rs
+++ b/lispers-core/src/lisp/eval.rs
@@ -1,10 +1,12 @@
 use std::fmt::Display;
 
+use crate::parser::ParserError;
+
 use super::environment::Environment;
 use super::environment::EnvironmentLayer;
 use super::expression::Expression;
 
-#[derive(Debug)]
+#[derive(Debug, Clone, PartialEq)]
 /// All possible evaluation errors
 pub enum EvalError {
     SymbolNotBound(String),
@@ -14,6 +16,7 @@ pub enum EvalError {
     TypeError(String),
     NotASymbol(Expression),
     RuntimeError(String),
+    ParserError(ParserError),
 }
 
 impl Display for EvalError {
@@ -26,6 +29,7 @@ impl Display for EvalError {
             EvalError::TypeError(s) => write!(f, "Type error: {}", s),
             EvalError::NotASymbol(e) => write!(f, "Expression {} is not a symbol", e),
             EvalError::RuntimeError(s) => write!(f, "Runtime error: {}", s),
+            EvalError::ParserError(s) => write!(f, "Parser error: {}", s),
         }
     }
 }
diff --git a/lispers-core/src/parser/parser.rs b/lispers-core/src/parser/parser.rs
index a5ed319..af28cf2 100644
--- a/lispers-core/src/parser/parser.rs
+++ b/lispers-core/src/parser/parser.rs
@@ -3,6 +3,7 @@ use super::tokenizer::tokenize;
 use super::tokenizer::TokenStream;
 use super::tokenizer::TokenizerError;
 use crate::lisp::Expression;
+use std::fmt::Display;
 use std::iter::Peekable;
 
 #[derive(Debug, Clone, PartialEq)]
@@ -18,6 +19,16 @@ impl From<TokenizerError> for ParserError {
     }
 }
 
+impl Display for ParserError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            ParserError::TokenizerError(t) => write!(f, "Tokenizer Error: {}", t),
+            ParserError::UnexpectedToken(t) => write!(f, "Unexpecte Token: {}", t),
+            ParserError::UnexpectedEndOfInput => write!(f, "Unexpected end of input."),
+        }
+    }
+}
+
 fn parse_list<I>(stream: &mut Peekable<TokenStream<I>>) -> Result<Expression, ParserError>
 where
     I: Iterator<Item = char>,
diff --git a/lispers-core/src/parser/token.rs b/lispers-core/src/parser/token.rs
index 4d7643a..3209663 100644
--- a/lispers-core/src/parser/token.rs
+++ b/lispers-core/src/parser/token.rs
@@ -1,3 +1,5 @@
+use std::fmt::Display;
+
 #[derive(Debug, PartialEq, Clone)]
 /// Sum type of different tokens
 pub enum Token {
@@ -12,3 +14,20 @@ pub enum Token {
     Symbol(String),
     True,
 }
+
+impl Display for Token {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Token::FloatLiteral(x) => write!(f, "{}", x),
+            Token::IntLiteral(x) => write!(f, "{}", x),
+            Token::Dot => write!(f, "."),
+            Token::Nil => write!(f, "nil"),
+            Token::ParClose => write!(f, ")"),
+            Token::ParOpen => write!(f, "("),
+            Token::Quote => write!(f, "'"),
+            Token::StringLiteral(x) => write!(f, "\"{}\"", x),
+            Token::Symbol(x) => write!(f, "{}", x),
+            Token::True => write!(f, "true"),
+        }
+    }
+}
diff --git a/lispers-core/src/parser/tokenizer.rs b/lispers-core/src/parser/tokenizer.rs
index 466c9be..cc46d26 100644
--- a/lispers-core/src/parser/tokenizer.rs
+++ b/lispers-core/src/parser/tokenizer.rs
@@ -1,3 +1,5 @@
+use std::fmt::Display;
+
 use super::token::Token;
 
 #[derive(Debug, Clone, PartialEq)]
@@ -7,6 +9,14 @@ pub enum TokenizerError {
     UnmatchedSequence(String),
 }
 
+impl Display for TokenizerError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TokenizerError::UnmatchedSequence(s) => write!(f, "Unmatched sequence: {}", s),
+        }
+    }
+}
+
 /// A reader used to wrap the `TokenStream`.
 /// When reading, it starts with the staging buffer of the stream, once
 /// it's end is reached, the input stream is copied character wise to