rational_tools.cpp

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/*******************************************************************\
 
Module: Rational Numbers
 
Author: Daniel Kroening, kroening@kroening.com
 
\*******************************************************************/
 
 
#include "rational_tools.h"
 
#include "mathematical_types.h"
#include "rational.h"
 
static mp_integer power10(size_t i)
{
  mp_integer result=1;
 
  for(; i!=0; i--)
    result*=10;
 
  return result;
}
 
bool to_rational(const exprt &expr, rationalt &rational_value)
{
  if(expr.id()!=ID_constant)
    return true;
 
  const std::string &value=expr.get_string(ID_value);
 
  std::string no1, no2;
  char mode=0;
 
  for(const char ch : value)
  {
    if(isdigit(ch))
    {
      if(mode==0)
        no1+=ch;
      else
        no2+=ch;
    }
    else if(ch=='/' || ch=='.')
    {
      if(mode==0)
        mode=ch;
      else
        return true;
    }
    else
      return true;
  }
 
  switch(mode)
  {
  case 0:
    rational_value=rationalt(string2integer(no1));
    break;
 
  case '.':
    rational_value=rationalt(string2integer(no1));
    rational_value+=
      rationalt(string2integer(no2))/rationalt(power10(no2.size()));
    break;
 
  case '/':
    rational_value=rationalt(string2integer(no1));
    rational_value/=rationalt(string2integer(no2));
    break;
 
  default:
    return true;
  }
 
  return false;
}
 
constant_exprt from_rational(const rationalt &a)
{
  std::string d=integer2string(a.get_numerator());
  if(a.get_denominator()!=1)
    d+="/"+integer2string(a.get_denominator());
  return constant_exprt(d, rational_typet());
}