Tweaked the error message a bit

Operation.h

@@ -1,3 +1,5 @@
+#pragma once
+
 enum class OpType
 {
     Addition, Subtraction, Multiplication, Division, Modulo, Special

basecalc.cpp

@@ -1,4 +1,5 @@
 #include "basecalc.h"
+#include <iostream>
 
 BaseCalculator::~BaseCalculator()
 {}
@@ -20,11 +21,23 @@ int BaseCalculator::calculate(const Operation& op)
         break;
 
         case OpType::Division:
-        result = op.a / op.b;
+        if (op.b == 0)
+        {
+            std::cerr << "Invalid operation requested! Resetting the accumulator to 0\n";
+            result = 0;
+        }
+        else
+            result = op.a / op.b;
         break;
 
         case OpType::Modulo:
-        result += op.a % op.b;
+        if (op.b == 0)
+        {
+            std::cerr << "Invalid operation requested! Resetting the accumulator to 0\n";
+            result = 0;
+        }
+        else
+            result = op.a % op.b;
         break;
 
         case OpType::Special:

basecalc.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "Operation.h"
 class BaseCalculator
 {

command.h

@@ -1,3 +1,5 @@
+#pragma once
+
 class Command
 {
     public:

input_resolver.cpp

@@ -1,6 +1,7 @@
 #include "input_resolver.h"
 #include <string>
 #include <iostream>
+#include <sstream>
 
 #define delimiter " "
 
@@ -63,12 +64,14 @@ Command resolveCommand()
     auto validation_result = validate_token(token);
     if (!validation_result.ok())
     {
-        throw std::runtime_error{"invalid token " + validation_result.incorrect_token()};
+        std::ostringstream os;
+        os << "invalid token "<< validation_result.incorrect_token();
+        throw std::runtime_error{os.str()};
     }
 
     bool shouldQuit = token.find("q") != token.npos;
     bool shouldPrint = token.find("p") != token.npos;
-    char operation;
+    char operation = 0;
 
     for (const char c: token)
     {
@@ -79,5 +82,10 @@ Command resolveCommand()
         }
     }
 
+    if (operation == 0)
+    {
+        operation = '+';
+    }
+
     return {shouldQuit, operation, validation_result.next_arg(), shouldPrint};
 }

input_resolver.h

@@ -1,2 +1,4 @@
+#pragma once
+
 #include "command.h"
 Command resolveCommand();

main.cpp

@@ -6,13 +6,13 @@
 
 int main()
 {
-    auto calc = std::make_unique<BaseCalculator>();
+    std::unique_ptr<BaseCalculator> calc = std::make_unique<SpecialCalculator>();
 
-    std::cout << "Initializing calculator";
+    std::cout << "Initializing calculator\n";
 
     while (true)
     {
-        std::cout << "What's your next input? (+,-,*,/,%,$,q,p)";
+        std::cout << "What's your next input? (+,-,*,/,%,$,q,p): ";
         auto command = resolveCommand();
 
         if (command.shouldTerminate())

special_calculator.h

@@ -1,3 +1,5 @@
+#pragma once
+
 #include "basecalc.h"
 
 class SpecialCalculator: public BaseCalculator