Bump required CMake version to 3.13 and make target source paths private and relative

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.8)
+cmake_minimum_required(VERSION 3.13)
 project(calculator CXX)
 set(CMAKE_CXX_STANDARD 17)
 

README.md

@@ -40,7 +40,7 @@ Prerequisites:
 
 ### On macOS/Linux
 Prerequisites:
-- CMake 3.8 or newer
+- CMake 3.13 or newer
 - C++17-compatible compiler, e.g. GCC 7 or Clang 4
 
 - Create a new directory named `cmake_build` in the repository folder

src/CalcManager/CEngine/CMakeLists.txt

@@ -1,14 +1,14 @@
-target_sources(CalcManager PUBLIC
-	CEngine/calc.cpp
-	CEngine/CalcInput.cpp
-	CEngine/CalcUtils.cpp
-	CEngine/History.cpp
-	CEngine/Number.cpp
-	CEngine/Rational.cpp
-	CEngine/RationalMath.cpp
-	CEngine/scicomm.cpp
-	CEngine/scidisp.cpp
-	CEngine/scifunc.cpp
-	CEngine/scioper.cpp
-	CEngine/sciset.cpp
+target_sources(CalcManager PRIVATE
+	calc.cpp
+	CalcInput.cpp
+	CalcUtils.cpp
+	History.cpp
+	Number.cpp
+	Rational.cpp
+	RationalMath.cpp
+	scicomm.cpp
+	scidisp.cpp
+	scifunc.cpp
+	scioper.cpp
+	sciset.cpp
 )

src/CalcManager/Ratpack/CMakeLists.txt

@@ -1,14 +1,14 @@
-target_sources(CalcManager PUBLIC
-	Ratpack/basex.cpp
-	Ratpack/conv.cpp
-	Ratpack/exp.cpp
-	Ratpack/fact.cpp
-	Ratpack/itrans.cpp
-	Ratpack/itransh.cpp
-	Ratpack/logic.cpp
-	Ratpack/num.cpp
-	Ratpack/rat.cpp
-	Ratpack/support.cpp
-	Ratpack/trans.cpp
-	Ratpack/transh.cpp
+target_sources(CalcManager PRIVATE
+	basex.cpp
+	conv.cpp
+	exp.cpp
+	fact.cpp
+	itrans.cpp
+	itransh.cpp
+	logic.cpp
+	num.cpp
+	rat.cpp
+	support.cpp
+	trans.cpp
+	transh.cpp
 )