exprtk_nthroot_bisection.cpp File Reference

#include <cmath>
#include <cstdio>
#include <string>
#include "exprtk.hpp"

Include dependency graph for exprtk_nthroot_bisection.cpp:

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Functions
template<typename T >
void	nthroot_via_bisection ()
int	main ()

Function Documentation

main()

int main

(

)

Definition at line 89 of file exprtk_nthroot_bisection.cpp.

{
   nthroot_via_bisection<double>();
   return 0;
}

nthroot_via_bisection()

template<typename T >

void nthroot_via_bisection

(

)

Definition at line 28 of file exprtk_nthroot_bisection.cpp.

{
   typedef exprtk::symbol_table<T>         symbol_table_t;
   typedef exprtk::expression<T>           expression_t;
   typedef exprtk::parser<T>               parser_t;
   typedef exprtk::function_compositor<T>  compositor_t;
   typedef typename compositor_t::function function_t;
 
   const std::string nthroot_via_bisection_program =
      " for (var x := -30; x <= 30; x += 1)   "
      " {                                     "
      "    println('[', x, ']',               "
      "            ' sqrt = ', nthroot(x,2),  "
      "            ' cbrt = ', nthroot(x,3)); "
      " }                                     ";
 
   exprtk::rtl::io::println<T> println;
 
   symbol_table_t symbol_table;
   symbol_table.add_function("println",println);
 
   compositor_t compositor(symbol_table);
 
   // define function: nthroot(x,n)
   compositor.add(
      function_t("nthroot")
      .var("x")
      .var("n")
      .expression
      (
        " if (abs(frac(n)) > 0)            "
        "    return [null];                "
        " else if (x < 0 and (n % 2 == 0)) "
        "    return [null];                "
        "                                  "
        " var lo := min(0,x);              "
        " var hi := max(0,x);              "
        "                                  "
        " while (true)                     "
        " {                                "
        "    var mid := avg(lo,hi);        "
        "    var y   := pow(mid,n);        "
        "                                  "
        "    if (equal(y, x))              "
        "       break [mid];               "
        "    else if (y < x)               "
        "       lo := mid;                 "
        "    else                          "
        "       hi := mid;                 "
        " };                               "
       ));
 
   expression_t expression;
   expression.register_symbol_table(symbol_table);
 
   parser_t parser;
   parser.compile(nthroot_via_bisection_program, expression);
 
   expression.value();
}