#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <ctype.h>

using namespace std;

struct element
{ string symbol;
  double atwt;
  string name; };

int initialise(element t[]);
double find_at_wt(string sym, element tab[], int max);
string find_name(string sym, element tab[], int max);

struct mystream
{ string line;
  int pos; };

void initialise(mystream & ms, string x)
{ ms.line = x;
  ms.pos = 0; }

void report(string info, mystream ms)
{ cout << info << ", Mystream: already gone '";
  for (int i=0; i<ms.pos; i+=1)
    cout << ms.line[i];
  cout << "', still to read '";
  for (int i=ms.pos; i<ms.line.length(); i+=1)
    cout << ms.line[i];
  cout << "'\n"; }

bool empty(mystream ms)
{ if (ms.pos >= ms.line.length())
    return true;
  else
    return false; }

char sneak_next_char(mystream ms)
{ if (empty(ms))
    return '.'; 
  else
    return ms.line[ms.pos]; }

char get_next_char(mystream & ms)
{ if (empty(ms))
    return '.'; 
  else
  { char answer = ms.line[ms.pos];
    ms.pos += 1;
    return answer; } }

string tostring(char c)
{ string answer = "";
  answer += c;
  return answer; }

string get_next_symbol(mystream & str)
{ if (isupper(sneak_next_char(str)))
  { string answer = tostring(get_next_char(str));
    if (islower(sneak_next_char(str)))
      answer += get_next_char(str);
    return answer; }
  else
    return "Error!!!!!!!!"; }

int get_next_number(mystream & str)
{ int total = 0;
  while (isdigit(sneak_next_char(str)))
  { char c = get_next_char(str);
    total = total * 10 + digittoint(c); }
  return total; }

double find_mol_wt(mystream & mystr, element tab[], int max)
{ double total = 0.0;
report("before loop", mystr);
  while (! empty(mystr))
  { string atom = get_next_symbol(mystr);
report("in loop", mystr);
    double aw = find_at_wt(atom, tab, max);
    cout << atom << "(" << find_name(atom, tab, max) << "): " << aw;
    if (isdigit(sneak_next_char(mystr)))
    { int num = get_next_number(mystr);
      aw *= num;
      cout << " x " << num << " = " << aw; }
    cout << "\n";
    total+=aw; }
  return total; }

void main()
{ element table[110];
  int numelems = initialise(table);
  while (true)
  { cout << "Formula? ";
    string e;
    cin >> e;
    if (cin.fail())
      break;
    mystream min;
    initialise(min, e);
    cout << find_mol_wt(min, table, numelems) << "\n"; } }

void set(element & e, string s, double a, string n)
{ e.symbol=s;
  e.atwt=a;
  e.name=n; }

double find_at_wt(string sym, element tab[], int max)
{ for (int en=1; en<=max; en+=1)
  { if (tab[en].symbol == sym)
      return tab[en].atwt; }
  cout << "error symbol " << sym << "\n";
  return -99999.9; }

string find_name(string sym, element tab[], int max)
{ for (int en=1; en<=max; en+=1)
  { if (tab[en].symbol == sym)
      return tab[en].name; }
  cout << "error symbol " << sym << "\n";
  return "Error!!!"; }

int initialise(element t[])
{ set(t[1], "H", 1.00794, "Hydrogen");
  set(t[2], "He", 4.002602, "Helium");
  set(t[3], "Li", 6.941, "Lithium");
  set(t[4], "Be", 9.012182, "Beryllium");
  set(t[5], "B", 10.811, "Boron");
  set(t[6], "C", 12.0107, "Carbon");
  set(t[7], "N", 14.0067, "Nitrogen");
  set(t[8], "O", 15.9994, "Oxygen");
  set(t[9], "F", 18.9984032, "Fluorine");
  set(t[10], "Ne", 20.1797, "Neon");
  set(t[11], "Na", 22.98976928, "Sodium");
  set(t[12], "Mg", 24.3050, "Magnesium");
  set(t[13], "Al", 26.9815386, "Aluminium");
  set(t[14], "Si", 28.0855, "Silicon");
  set(t[15], "P", 30.973762, "Phosphorus");
  set(t[16], "S", 32.065, "Sulfur");
  set(t[17], "Cl", 35.453, "Chlorine");
  set(t[18], "Ar", 39.948, "Argon");
  set(t[19], "K", 39.0983, "Potassium");
  set(t[20], "Ca", 40.078, "Calcium");
  set(t[21], "Sc", 44.955912, "Scandium");
  set(t[22], "Ti", 47.867, "Titanium");
  set(t[23], "V", 50.9415, "Vanadium");
  set(t[24], "Cr", 51.9961, "Chromium");
  set(t[25], "Mn", 54.938045, "Manganese");
  set(t[26], "Fe", 55.845, "Iron");
  set(t[27], "Co", 58.933195, "Cobalt");
  set(t[28], "Ni", 58.6934, "Nickel");
  set(t[29], "Cu", 63.546, "Copper");
  set(t[30], "Zn", 65.38, "Zinc");
  set(t[31], "Ga", 69.723, "Gallium");
  set(t[32], "Ge", 72.64, "Germanium");
  set(t[33], "As", 74.92160, "Arsenic");
  set(t[34], "Se", 78.96, "Selenium");
  set(t[35], "Br", 79.904, "Bromine");
  set(t[36], "Kr", 83.798, "Krypton");
  set(t[37], "Rb", 85.4678, "Rubidium");
  set(t[38], "Sr", 87.62, "Strontium");
  set(t[39], "Y", 88.90585, "Yttrium");
  set(t[40], "Zr", 91.224, "Zirconium");
  set(t[41], "Nb", 92.90638, "Niobium");
  set(t[42], "Mo", 95.96, "Molybdenum");
  set(t[43], "Tc", 98, "Technetium");
  set(t[44], "Ru", 101.07, "Ruthenium");
  set(t[45], "Rh", 102.90550, "Rhodium");
  set(t[46], "Pd", 106.42, "Palladium");
  set(t[47], "Ag", 107.8682, "Silver");
  set(t[48], "Cd", 112.411, "Cadmium");
  set(t[49], "In", 114.818, "Indium");
  set(t[50], "Sn", 118.710, "Tin");
  set(t[51], "Sb", 121.760, "Antimony");
  set(t[52], "Te", 127.60, "Tellurium");
  set(t[53], "I", 126.90447, "Iodine");
  set(t[54], "Xe", 131.293, "Xenon");
  set(t[55], "Cs", 132.9054519, "Caesium");
  set(t[56], "Ba", 137.327, "Barium");
  set(t[57], "La", 138.90547, "Lanthanum");
  set(t[58], "Ce", 140.116, "Cerium");
  set(t[59], "Pr", 140.90765, "Praseodymium");
  set(t[60], "Nd", 144.242, "Neodymium");
  set(t[61], "Pm", 145, "Promethium");
  set(t[62], "Sm", 150.36, "Samarium");
  set(t[63], "Eu", 151.964, "Europium");
  set(t[64], "Gd", 157.25, "Gadolinium");
  set(t[65], "Tb", 158.92535, "Terbium");
  set(t[66], "Dy", 162.500, "Dysprosium");
  set(t[67], "Ho", 164.93032, "Holmium");
  set(t[68], "Er", 167.259, "Erbium");
  set(t[69], "Tm", 168.93421, "Thulium");
  set(t[70], "Yb", 173.054, "Ytterbium");
  set(t[71], "Lu", 174.9668, "Lutetium");
  set(t[72], "Hf", 178.49, "Hafnium");
  set(t[73], "Ta", 180.94788, "Tantalum");
  set(t[74], "W", 183.84, "Tungsten");
  set(t[75], "Re", 186.207, "Rhenium");
  set(t[76], "Os", 190.23, "Osmium");
  set(t[77], "Ir", 192.217, "Iridium");
  set(t[78], "Pt", 195.084, "Platinum");
  set(t[79], "Au", 196.966569, "Gold");
  set(t[80], "Hg", 200.59, "Mercury");
  set(t[81], "Tl", 204.3833, "Thallium");
  set(t[82], "Pb", 207.2, "Lead");
  set(t[83], "Bi", 208.98040, "Bismuth");
  set(t[84], "Po", 209, "Polonium");
  set(t[85], "At", 210, "Astatine");
  set(t[86], "Rn", 222, "Radon");
  set(t[87], "Fr", 223, "Francium");
  set(t[88], "Ra", 226, "Radium");
  set(t[89], "Ac", 227, "Actinium");
  set(t[90], "Th", 232.03806, "Thorium");
  set(t[91], "Pa", 231.03588, "Protactinium");
  set(t[92], "U", 238.02891, "Uranium");
  set(t[93], "Np", 237, "Neptunium");
  set(t[94], "Pu", 244, "Plutonium");
  set(t[95], "Am", 243, "Americium");
  set(t[96], "Cm", 247, "Curium");
  set(t[97], "Bk", 247, "Berkelium");
  set(t[98], "Cf", 251, "Californium");
  set(t[99], "Es", 252, "Einsteinium");
  set(t[100], "Fm", 257, "Fermium");
  set(t[101], "Md", 258, "Mendelevium");
  set(t[102], "No", 259, "Nobelium");
  set(t[103], "Lr", 262, "Lawrencium");
  set(t[104], "Rf", 267, "Rutherfordium");
  return 104; }