My program always comes back as true, instead of requiring only 1 decimal point.

Question

My program always comes back as true, instead of requiring only 1 decimal point. I can't figure out why. Help?

9. (Useful utility) a. Write a C++ function named isvalidreal) that checks for a valid dou ble-precision number. This kind of number can have an optional + or - sign, at most one decimal point (which can be the first character), and at least one digit between 0 and 9. The function should return a Boolean value of true if the entered number is a real number; other- wise, it should return a Boolean value of false.

Explanation / Answer

Everything is well and good except one thing:

you have checked for the presence of "." but do not store it anywhere. Anyway, i have modified your code, go through it, run it nad check it with al the possible cases.if there will be any problem, please rply us.

Thank you.

My program:

#include<iostream>
#include<string>
#include<stdlib.h>
using namespace std;
int main()
{
   bool isValidReal(string);
   string value;
   double number;
   cout<<"enter the value: ";
   cin>>value;
   if(!isValidReal(value))
   {
       cout<<"number is not real ";
   }
   else
   {
       number=atof(value.c_str());
       cout<<"the number you entered is"<<number;
   }
   system("pause");
   return 0;
}

bool isValidReal(string str)
{ int count_point=0;
   int start=0,i;
   bool valid=true;
   bool sign=false;
   bool have_point=false;
   if(int(str.length())==0)
   {
       valid=false;
   }
   if(str.at(0)=='-'||str.at(0)=='+')
   {
       sign=true;
       start=1;
   }
   if(sign&&int((str.length())==1))
   valid=false;
   i=start;
   while(valid&& i< int(str.length()))
   {
       if(!isdigit(str.at(i)))
       valid=false;
       if(str.at(i)=='.')
       {
       have_point=true;
       count_point++;
       valid=true;
   }
       i++;
   }
   if(have_point&&valid&&count_point==1)
   return true;
   else
   return false;
}

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