diff options
Diffstat (limited to 'Help/guide/tutorial/Step2')
-rw-r--r-- | Help/guide/tutorial/Step2/CMakeLists.txt | 23 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/MathFunctions/CMakeLists.txt | 1 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/MathFunctions/MathFunctions.h | 1 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/MathFunctions/mysqrt.cxx | 23 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/TutorialConfig.h.in | 3 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/directions.txt | 101 | ||||
-rw-r--r-- | Help/guide/tutorial/Step2/tutorial.cxx | 23 |
7 files changed, 175 insertions, 0 deletions
diff --git a/Help/guide/tutorial/Step2/CMakeLists.txt b/Help/guide/tutorial/Step2/CMakeLists.txt new file mode 100644 index 0000000..8e50e7c --- /dev/null +++ b/Help/guide/tutorial/Step2/CMakeLists.txt @@ -0,0 +1,23 @@ +cmake_minimum_required(VERSION 3.3) +project(Tutorial) + +set(CMAKE_CXX_STANDARD 14) +# the version number. +set(Tutorial_VERSION_MAJOR 1) +set(Tutorial_VERSION_MINOR 0) + +# configure a header file to pass some of the CMake settings +# to the source code +configure_file( + "${PROJECT_SOURCE_DIR}/TutorialConfig.h.in" + "${PROJECT_BINARY_DIR}/TutorialConfig.h" + ) + +# add the executable +add_executable(Tutorial tutorial.cxx) + +# add the binary tree to the search path for include files +# so that we will find TutorialConfig.h +target_include_directories(Tutorial PUBLIC + "${PROJECT_BINARY_DIR}" + ) diff --git a/Help/guide/tutorial/Step2/MathFunctions/CMakeLists.txt b/Help/guide/tutorial/Step2/MathFunctions/CMakeLists.txt new file mode 100644 index 0000000..8b443a6 --- /dev/null +++ b/Help/guide/tutorial/Step2/MathFunctions/CMakeLists.txt @@ -0,0 +1 @@ +add_library(MathFunctions mysqrt.cxx) diff --git a/Help/guide/tutorial/Step2/MathFunctions/MathFunctions.h b/Help/guide/tutorial/Step2/MathFunctions/MathFunctions.h new file mode 100644 index 0000000..cd36bcc --- /dev/null +++ b/Help/guide/tutorial/Step2/MathFunctions/MathFunctions.h @@ -0,0 +1 @@ +double mysqrt(double x); diff --git a/Help/guide/tutorial/Step2/MathFunctions/mysqrt.cxx b/Help/guide/tutorial/Step2/MathFunctions/mysqrt.cxx new file mode 100644 index 0000000..7d9379e --- /dev/null +++ b/Help/guide/tutorial/Step2/MathFunctions/mysqrt.cxx @@ -0,0 +1,23 @@ +#include "MathFunctions.h" +#include <iostream> + +// a hack square root calculation using simple operations +double mysqrt(double x) +{ + if (x <= 0) { + return 0; + } + + double result = x; + + // do ten iterations + for (int i = 0; i < 10; ++i) { + if (result <= 0) { + result = 0.1; + } + double delta = x - (result * result); + result = result + 0.5 * delta / result; + std::cout << "Computing sqrt of " << x << " to be " << result << std::endl; + } + return result; +} diff --git a/Help/guide/tutorial/Step2/TutorialConfig.h.in b/Help/guide/tutorial/Step2/TutorialConfig.h.in new file mode 100644 index 0000000..7e4d7fa --- /dev/null +++ b/Help/guide/tutorial/Step2/TutorialConfig.h.in @@ -0,0 +1,3 @@ +// the configured options and settings for Tutorial +#define Tutorial_VERSION_MAJOR @Tutorial_VERSION_MAJOR@ +#define Tutorial_VERSION_MINOR @Tutorial_VERSION_MINOR@ diff --git a/Help/guide/tutorial/Step2/directions.txt b/Help/guide/tutorial/Step2/directions.txt new file mode 100644 index 0000000..48de7a2 --- /dev/null +++ b/Help/guide/tutorial/Step2/directions.txt @@ -0,0 +1,101 @@ +# Adding a Library # + +Now we will add a library to our project. This library will contain our own +implementation for computing the square root of a number. The executable can +then use this library instead of the standard square root function provided by +the compiler. + +For this tutorial we will put the library into a subdirectory +called MathFunctions. It will have the following one line CMakeLists file: + + add_library(MathFunctions mysqrt.cxx) + +The source file mysqrt.cxx has one function called mysqrt that provides similar +functionality to the compiler’s sqrt function. To make use of the new library +we add an add_subdirectory call in the top-level CMakeLists file so that the +library will get built. We add the new library to the executable, and add the +MathFunctions as an include directory so that mqsqrt.h header file can be +found. The last few lines of the top-level CMakeLists file now look like: + + + add_subdirectory(MathFunctions) + + #add the executable + add_executable(Tutorial tutorial.cxx) + + target_link_libraries(Tutorial ${EXTRA_LIBS}) + + +Now let us make the MathFunctions library optional. While for the tutorial +there really isn’t any need to do so, but with larger projects this is a common +occurrence. The first step is to add an option to the top-level CMakeLists file. + + option (USE_MYMATH + "Use tutorial provided math implementation" ON) + +This will show up in CMake GUI and ccmake with a default value of ON that can +be changed by the user. This setting will be stored so that the user does not +need to set the value each time they run CMake on this build directory. + +The next change is to make building and linking the MathFunctions library +conditional. To do this we change the top-level CMakeLists file to look like +the following: + + cmake_minimum_required(VERSION 3.3) + project(Tutorial) + + set(CMAKE_CXX_STANDARD 14) + + # the version number. + set(Tutorial_VERSION_MAJOR 1) + set(Tutorial_VERSION_MINOR 0) + + # configure a header file to pass some of the CMake settings + # to the source code + configure_file( + "${PROJECT_SOURCE_DIR}/TutorialConfig.h.in" + "${PROJECT_BINARY_DIR}/TutorialConfig.h" + ) + + # should we use our own math functions + option(USE_MYMATH "Use tutorial provided math implementation" ON) + + # add the MathFunctions library? + if(USE_MYMATH) + add_subdirectory(MathFunctions) + list(APPEND EXTRA_LIBS MathFunctions) + list(APPEND EXTRA_INCLUDES "${PROJECT_SOURCE_DIR}/MathFunctions") + endif(USE_MYMATH) + + # add the executable + add_executable(Tutorial tutorial.cxx) + + target_link_libraries(Tutorial ${EXTRA_LIBS}) + + # add the binary tree to the search path for include files + # so that we will find TutorialConfig.h + target_include_directories(Tutorial PUBLIC + "${PROJECT_BINARY_DIR}" + ${EXTRA_INCLUDES} + ) + +Note the use of the variables EXTRA_LIBS, and EXTRA_INCLUDES to collect +up any optional libraries to later be linked into the executable. This is a +classic approach when dealing with many optional components, we will cover the +modern approach in the next step. For now the corresponding changes to the +source code are fairly straightforward and leave us with: + + #ifdef USE_MYMATH + double outputValue = mysqrt(inputValue); + #else + double outputValue = sqrt(inputValue); + #endif + +Since the source code now requires USE_MYMATH we can add it to the +TutorialConfig.h.in. Simply add the following line: + #cmakedefine USE_MYMATH + +Run cmake or cmake-gui to configure the project and then build it with your +chosen build tool and then run the built Tutorial executable. + +Which function gives better results, Step1’s sqrt or Step2’s mysqrt? diff --git a/Help/guide/tutorial/Step2/tutorial.cxx b/Help/guide/tutorial/Step2/tutorial.cxx new file mode 100644 index 0000000..5ba34e8 --- /dev/null +++ b/Help/guide/tutorial/Step2/tutorial.cxx @@ -0,0 +1,23 @@ +// A simple program that computes the square root of a number +#include <cmath> +#include <iostream> +#include <string> + +#include "TutorialConfig.h" + +int main(int argc, char* argv[]) +{ + if (argc < 2) { + std::cout << argv[0] << " Version " << Tutorial_VERSION_MAJOR << "." + << Tutorial_VERSION_MINOR << std::endl; + std::cout << "Usage: " << argv[0] << " number" << std::endl; + return 1; + } + + double inputValue = std::stod(argv[1]); + + double outputValue = sqrt(inputValue); + std::cout << "The square root of " << inputValue << " is " << outputValue + << std::endl; + return 0; +} |