can now parse identifiers and integer literals

src/ast/expressions/integer.cpp

@@ -0,0 +1,15 @@
+#include "integer.hpp"
+
+namespace ast {
+    integer_literal::integer_literal(token::token token, int value)
+        : token(std::move(token)),
+          value(value) {}
+
+    std::string integer_literal::token_literal() const {
+        return token.literal;
+    };
+
+    std::string integer_literal::str() const {
+        return token.literal;
+    };
+} // namespace ast

src/ast/expressions/integer.hpp

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "ast/ast.hpp"
+#include "token/token.hpp"
+
+namespace ast {
+    struct integer_literal : expression {
+        integer_literal(token::token token, int value);
+        token::token token;
+        int value;
+
+        std::string token_literal() const override;
+        std::string str() const override;
+    };
+} // namespace ast

src/parser/parser.cpp

@@ -1,5 +1,9 @@
 #include "parser.hpp"
 
+#include "ast/expressions/identifier.hpp"
+#include "ast/expressions/integer.hpp"
+#include "token/type.hpp"
+
 #include <sstream>
 
 namespace parser {
@@ -9,6 +13,16 @@ namespace parser {
           next(token::type::ILLEGAL, "") {
         next_token();
         next_token();
+
+        register_prefix(
+            token::type::IDENTIFIER,
+            std::bind(&parser::parse_identifier, this)
+        );
+
+        register_prefix(
+            token::type::INT,
+            std::bind(&parser::parse_integer, this)
+        );
     }
 
     void parser::next_token() {
@@ -45,11 +59,13 @@ namespace parser {
         }
     }
 
-    ast::expression* parser::parse_expression() {
-        // TODO: we are currently skipping expressions until we encounter a
-        // semicolon
-        for (; current.type != token::type::SEMICOLON; next_token()) {}
-        return nullptr;
+    ast::expression* parser::parse_expression(precedence) {
+        auto it = prefix_parse_fns.find(current.type);
+        if (it == prefix_parse_fns.end())
+            return nullptr;
+
+        prefix_parse_fn func = it->second;
+        return func();
     };
 
     ast::return_stmt* parser::parse_return() {
@@ -126,4 +142,12 @@ namespace parser {
     void parser::register_infix(token::type type, infix_parse_fn fn) {
         infix_parse_fns[type] = fn;
     };
+
+    ast::expression* parser::parse_identifier() {
+        return new ast::identifier(current, current.literal);
+    };
+
+    ast::expression* parser::parse_integer() {
+        return new ast::integer_literal(current, std::stoi(current.literal));
+    };
 } // namespace parser

src/parser/parser.hpp

@@ -7,6 +7,7 @@
 #include "ast/statements/let.hpp"
 #include "ast/statements/return.hpp"
 #include "lexer/lexer.hpp"
+#include "precedence.hpp"
 #include "token/token.hpp"
 
 #include <functional>
@@ -18,7 +19,7 @@ namespace parser {
     using infix_parse_fn = std::function<ast::expression*(ast::expression*)>;
 
     struct parser {
-        parser(lexer::lexer& lexer);
+        parser(lexer::lexer&);
         ~parser();
         std::vector<ast::error::error*> errors;
 
@@ -34,7 +35,7 @@ namespace parser {
         void next_token();
         void skip_until_semicolon();
         ast::statement* parse_statement();
-        ast::expression* parse_expression();
+        ast::expression* parse_expression(precedence = precedence::LOWEST);
         ast::let_stmt* parse_let();
         ast::return_stmt* parse_return();
         ast::expression_stmt* parse_expression_stmt();
@@ -43,5 +44,8 @@ namespace parser {
 
         void register_prefix(token::type, prefix_parse_fn);
         void register_infix(token::type, infix_parse_fn);
+
+        ast::expression* parse_identifier();
+        ast::expression* parse_integer();
     };
 } // namespace parser

src/parser/precedence.hpp

@@ -0,0 +1,11 @@
+namespace parser {
+    enum class precedence {
+        LOWEST,
+        EQUALS,
+        LESS_GREATER,
+        SUM,
+        PRODUCT,
+        PREFIX,
+        CALL
+    };
+}