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input from command line example

October 26 2022 11:39:22.

 
 #if __has_include("iostream")
 #include <iostream>
 #define CXX
 #else
 #include <stdio.h>
 #include <stdlib.h>
 #endif
 
 int main(const int argc, const char* argv[])
 {
 #ifndef CXX // c 
 printf(" C version \n");
 #else // c++ 
 std::cout<<" C++ version" <<std::endl;
 #endif
 for(int i=0; i<argc; ++i)
 { 
 printf("input arg[%d]: \t %s \n",i,argv[i]);
 if(i>0)
 {
 // how to convert a char* to a numerical
 
 #ifndef CXX // c 
 const int n = atoi(argv[i]);
 printf("converted to int:\t %d \n",n);
 const double x = atof(argv[i]);
 printf("converted to double:\t %lf \n",x);
 //more robust cross-platform
 /* https://cplusplus.com/reference/cstdlib/strtol/ */
 const long int l = strtol(argv[i], NULL, 10);
 printf("converted to int:\t %ld \n",l);
 /* https://cplusplus.com/reference/cstdlib/strtod/ */
 const double y = strtod(argv[i], NULL);
 printf("converted to double:\t %lf \n",y);
 #else // c++ 
 const int m = std::stoi((argv[i]));
 std::cout<< "converted to int: \t" << m <<std::endl; 
 const double z = std::stod(std::string(argv[i]));
 std::cout<< "converted to double: \t" << z <<std::endl;
 // check what happens by passing a non-numeric
 #endif 
 } 
 } 
 return 0;
 }