diff options
Diffstat (limited to 'Help/guide/tutorial/Step6/MathFunctions')
4 files changed, 90 insertions, 0 deletions
diff --git a/Help/guide/tutorial/Step6/MathFunctions/CMakeLists.txt b/Help/guide/tutorial/Step6/MathFunctions/CMakeLists.txt new file mode 100644 index 0000000..f64c6ac --- /dev/null +++ b/Help/guide/tutorial/Step6/MathFunctions/CMakeLists.txt @@ -0,0 +1,32 @@ +add_library(MathFunctions mysqrt.cxx) + +# state that anybody linking to us needs to include the current source dir +# to find MathFunctions.h, while we don't. +target_include_directories(MathFunctions + INTERFACE ${CMAKE_CURRENT_SOURCE_DIR} + ) + +# does this system provide the log and exp functions? +include(CheckSymbolExists) +check_symbol_exists(log "math.h" HAVE_LOG) +check_symbol_exists(exp "math.h" HAVE_EXP) +if(NOT (HAVE_LOG AND HAVE_EXP)) + unset(HAVE_LOG CACHE) + unset(HAVE_EXP CACHE) + set(CMAKE_REQUIRED_LIBRARIES "m") + check_symbol_exists(log "math.h" HAVE_LOG) + check_symbol_exists(exp "math.h" HAVE_EXP) + if(HAVE_LOG AND HAVE_EXP) + target_link_libraries(MathFunctions PRIVATE m) + endif() +endif() + +# add compile definitions +if(HAVE_LOG AND HAVE_EXP) + target_compile_definitions(MathFunctions + PRIVATE "HAVE_LOG" "HAVE_EXP") +endif() + +# install rules +install(TARGETS MathFunctions DESTINATION lib) +install(FILES MathFunctions.h DESTINATION include) diff --git a/Help/guide/tutorial/Step6/MathFunctions/MakeTable.cxx b/Help/guide/tutorial/Step6/MathFunctions/MakeTable.cxx new file mode 100644 index 0000000..ee58556 --- /dev/null +++ b/Help/guide/tutorial/Step6/MathFunctions/MakeTable.cxx @@ -0,0 +1,25 @@ +// A simple program that builds a sqrt table +#include <cmath> +#include <fstream> +#include <iostream> + +int main(int argc, char* argv[]) +{ + // make sure we have enough arguments + if (argc < 2) { + return 1; + } + + std::ofstream fout(argv[1], std::ios_base::out); + const bool fileOpen = fout.is_open(); + if (fileOpen) { + fout << "double sqrtTable[] = {" << std::endl; + for (int i = 0; i < 10; ++i) { + fout << sqrt(static_cast<double>(i)) << "," << std::endl; + } + // close the table with a zero + fout << "0};" << std::endl; + fout.close(); + } + return fileOpen ? 0 : 1; // return 0 if wrote the file +} diff --git a/Help/guide/tutorial/Step6/MathFunctions/MathFunctions.h b/Help/guide/tutorial/Step6/MathFunctions/MathFunctions.h new file mode 100644 index 0000000..cd36bcc --- /dev/null +++ b/Help/guide/tutorial/Step6/MathFunctions/MathFunctions.h @@ -0,0 +1 @@ +double mysqrt(double x); diff --git a/Help/guide/tutorial/Step6/MathFunctions/mysqrt.cxx b/Help/guide/tutorial/Step6/MathFunctions/mysqrt.cxx new file mode 100644 index 0000000..0637063 --- /dev/null +++ b/Help/guide/tutorial/Step6/MathFunctions/mysqrt.cxx @@ -0,0 +1,32 @@ +#include <cmath> +#include <iostream> + +#include "MathFunctions.h" + +// a hack square root calculation using simple operations +double mysqrt(double x) +{ + if (x <= 0) { + return 0; + } + + // if we have both log and exp then use them +#if defined(HAVE_LOG) && defined(HAVE_EXP) + double result = exp(log(x) * 0.5); + std::cout << "Computing sqrt of " << x << " to be " << result + << " using log and exp" << std::endl; +#else + 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; + } +#endif + return result; +} |