Added a missing header file to main.cpp

Makefile

@@ -2,11 +2,11 @@ all:
 	cc command.cpp input_resolver.cpp main.cpp -lstdc++ -std=c++17 -O3 -L./ -lCalc -o calculator 
 
 libs:
-	cc -c -fPIC basecalc.cpp Operation.cpp
+	cc -c -fPIC basecalc.cpp Operation.cpp special_calculator.cpp
-	cc -shared basecalc.o Operation.o -o libCalc.so
+	cc -shared basecalc.o Operation.o special_calculator.o -o libCalc.so
 
 compile:
 	cc *.cpp -O3 -c
 
 debug:
-	cc *.cpp -g -std=c++17 -o calculator -lstdc++
+	cc *.cpp -g -std=c++17 -o calculator -lstdc++ -lm

main.cpp

@@ -1,5 +1,6 @@
 #include <iostream>
 #include "basecalc.h"
+#include "special_calculator.h"
 #include <memory>
 #include "input_resolver.h"