Trying a more object oriented approach and created an 'Object' struct to have metadata for the values the interpreter works with.

token.c

@@ -1,4 +1,6 @@
 #include "token.h"
+#include <stdlib.h>
+#include <string.h>
 
 KeyValuePair TokenTypeMappings[TOKENTYPE_MAPPINGS_COUNT] = {
     { "(", LParen}, { ")", RParen}, { ",", Comma }, { ".", Dot },
@@ -36,7 +38,7 @@ Token* CreateToken(const char* lexeme, void* literal, int line, TokenType type)
             return NULL;
         }
 
-        token->literal = mapping_result;
+        if (type != NIL) token->literal = mapping_result;
         token->lexeme = mapping_result;
     }
 
@@ -60,4 +62,32 @@ void FreeToken(Token* token) {
     if (token->type == String || token->type == Number || token->type == Identifier) free((void *) token->lexeme);
 
     free(token);
+}
+
+char* GetTokenStringValue(Token* token, int* length) {
+    length = 0;
+
+    if (!token) return NULL;
+    if (token->type != String) return NULL;
+
+    *length = strlen(token->lexeme);
+
+    if (length == 0) return NULL;
+
+    char* value = calloc(strlen(token->lexeme) + 1, sizeof(char));
+
+    strncpy(value, token->lexeme, *length);
+
+    return value;
+}
+
+int GetTokenNumberValue(Token* token, double* value) {
+    value = 0;
+
+    if (!token) return 0;
+    if (token->type != Number) return 0;
+
+    *value = *((double*)token->literal);
+
+    return 1;
 }