e.cpp

/****************
*Finding e to the Nth Digit
*By Tom Biju
****************/
#include <iostream>	
#include <iomanip>	//for setting precision
#include <stdlib.h> 
using namespace std;
//Program to find PI to a specified number of decimal places
int main(int argc, char* argv[]){
  double e=2.7182818284590452353602874713526624977572470936999595749669676277240766303535475945713821785251664274;	//e to 100 digits
  int decimalPlaces;			//integer variable to store the number of decimal places
  char* commandLine=argv[1];	//allows for user input from the command line
  if(commandLine==NULL){		//if nothing is entered on the command line, then...
  	cout<<"Enter how many decimal places of e you would like to see (limit 30):  "<<endl;	//prompt the user for the number of decimal places, up to 30
  	cin>>decimalPlaces;	//store the user input into the variable decimalPlaces
  	while(decimalPlaces<0||decimalPlaces>30){	//while loop to prompt user for new integer if a valid one was notentered
	  cout<<"Please enter an integer from 0-30"<<endl;
	  cin>>decimalPlaces;
  	}
  	decimalPlaces+=1;		//add one to the decimal places digits since the program starts with the one number before the decimal place
  }
  else{
	   decimalPlaces=atoi(commandLine);	//if something was entered on the command line, we will convert the string input into an integer
	    while(decimalPlaces<0||decimalPlaces>30){	//while loop if the input on the command line was not in the valid range
	 	 cout<<"Please enter an integer from 0-30"<<endl;
	 	 cin>>decimalPlaces;
 		}
	   decimalPlaces+=1;	//add one to account for the number before the decimal place
   }
  cout<<setprecision(decimalPlaces)<<e<<endl;	//display e to the number stored in decimalPlaces
  return 0;	//END
}