Added lexing and parsing for single quote

README.md

@@ -63,7 +63,7 @@ Woodpecker CI/CD system is integrated.
 Currently using Catch2 for unit testing.
 
 - Lexing - complete, more token types may be added as necessary
-- Parsing - This is the next step.
+- Parsing - the main steps are done, but things may change as time progresses
 - Optimizations - 
 - Emitting Bytecode - the goal.
 

src/include/lex.hpp

@@ -13,6 +13,7 @@ enum class TokenType {
     String,
     Int,
     Double,
+    Quote,
     End
 };
 

src/include/parse.hpp

@@ -20,6 +20,7 @@ private:
 
 
     std::optional<LispValue> parse_one();
+    LispValue parse_quote();
     LispValue parse_list();
 
 public:

src/include/value.hpp

@@ -1,11 +1,9 @@
 #pragma once
 
-#include <concepts>
 #include <deque>
 #include <cstdint>
 #include <string>
 #include <variant>
-#include <iostream>
 
 // we're using a pure variant as our value type.
 struct Integer {int64_t value;};

src/lex.cpp

@@ -12,6 +12,7 @@ std::ostream &operator<<(std::ostream &os, Token const &t) {
     case TokenType::OpenParen: os << "OpenParen)"; break;
     case TokenType::CloseParen: os << "CloseParen)"; break;
     case TokenType::Dollar: os << "Dollar)"; break;
+    case TokenType::Quote: os << "QUOTE)"; break;
     case TokenType::Symbol: os << "Symbol, " << get<string>(*t.value) << ")"; break;
     case TokenType::String: os << "String, \"" << get<string>(*t.value) << "\")"; break;
     case TokenType::Int: os << "Int, " << get<int64_t>(*t.value) << ")"; break;
@@ -139,6 +140,7 @@ Token Lexer::next() {
         case '(': return {TokenType::OpenParen, nullopt};
         case ')': return {TokenType::CloseParen, nullopt};
         case '$': return {TokenType::Dollar, nullopt};
+        case '\'': return {TokenType::Quote, nullopt};
         default:
             ss.unget();
             return lexNonSpecial();

src/parse.cpp

@@ -1,3 +1,4 @@
+#include <exception>
 #include <lex.hpp>
 
 #include <parse.hpp>
@@ -13,6 +14,10 @@ void Parser::feed(Lexer l) {
 }
 
 Token Parser::get_token() {
+    if (ts.empty()) {
+        cerr << "Parser::get_token: Token requested at input end." << endl;
+        throw exception();
+    }
     Token t = ts.front();
     ts.pop_front();
     return t;
@@ -29,6 +34,22 @@ Symbol Parser::make_symbol(string s) {
     return Symbol {s};
 }
 
+LispValue Parser::parse_quote() {
+    // in regular lisps, a quote gets expanded to a (quote) form.
+    // i.e. 'a is actually (QUOTE A). This prevents the symbol from being
+    // evaluated.
+    // This is the same way we'll handle quotes for now, because I can't
+    // think of anything else.
+    List l;
+
+    l.list.push_back(make_symbol("QUOTE"));
+    auto next = parse_one();
+    // this is guaranteed to work, because if we do not have enough tokens
+    // to constitute another value Parser::get_token will throw an exception
+    l.list.push_back(*next);
+    return l;
+}
+
 optional<LispValue> Parser::parse_one() {
     Token t = get_token();
     switch (t.type) {
@@ -38,6 +59,7 @@ optional<LispValue> Parser::parse_one() {
     case TokenType::Symbol: return make_symbol(get<string>(*t.value));
     case TokenType::OpenParen: return parse_list();
     case TokenType::CloseParen: throw "whatever";
+    case TokenType::Quote: return parse_quote();
 
     // I don't know what this will actually do, in theory maybe just like the OpenParen,
     // but parses things in a different namespace? unimplemented for now.

src/value.cpp

@@ -1,5 +1,6 @@
 #include <concepts>
 #include <value.hpp>
+#include <iostream>
 
 
 template <typename T>