#include <iostream>
#include <fstream>
#include <string>

using namespace std;

struct element
{ int atno;
  string sym, name;
  double atwt;

  element(int an, string sy, string nm, double aw)
  { atno = an;
    sym = sy;
    name = nm;
    atwt = aw; }

  element()
  { atno = 0;
    sym = "";
    name = "";
    atwt = 0; }

  void print()
  { cout << "(" << atno << ", " << atno << ", '"
         << sym << "', '" << name << "', " << atwt << ")"; } };

element makeel(int an, string sy, string nm, double aw)
{ element e;
  e.atno = an;
  e.sym = sy;
  e.name = nm;
  e.atwt = aw;
  return e; }

int read_table(element pt[])
{ ifstream inf;
  inf.open("/home/www/class/een118/a3010b.txt");
  if (inf.fail())
  { cerr << "Can't open file\n";
    exit(1); }
  int atno = 0;
  while (true)
  { string sym, name;
    double atwt;
    inf >> sym >> name >> atwt;
    if (inf.fail())
      break;
    atno += 1;
    element e(atno, sym, name, atwt);
    pt[atno] = e; }
  pt[0] = makeel(0, "XXX", "XXXXXXXXX", 0.0);
  inf.close();
  return atno; }

element findel(string sy, element pt[], int n)
{ for (int i = 1; i <= n; i += 1)
    if (pt[i].sym == sy)
      return pt[i];
  return pt[0]; }

string get_symbol()     // must only be called is next char is known to be a capital letter
{ char c1 = cin.get();
  char c2 = cin.peek();
  if (c2 < 'a' || c2 > 'z')
    return string("") + c1;
  cin.get();
  return string("") + c1 + c2; }

int get_number()        // must only be called if next char is know to be a digit
{ int value = 0;
  while (true)
  { char c = cin.peek();
    if (c < '0' || c > '9')
      return value;
    cin.get();    
    value = value * 10 + c - '0'; } }

int main()
{ string sym, name;
  double atwt;
  element pt[120];
  
  int atno = read_table(pt);
  
  const int entries = atno;
  for (atno = 1; atno <= entries; atno += 1)
  { pt[atno].print();
    cout << "\n"; }


  while (true)                     // spaces become a nuisance
  { bool bad = false;
    double molwt = 0;
    cout << "> ";
    while (true)
    { if (cin.peek() == '\n')
      { cin.get();
        break; }

      char nxt = cin.peek();
      if (c < 'A' || c > 'Z')
      { cout << "Element symbol expected but '" << c << "' seen\n";
        bad = true;
        break; }
      sym = get_symbol();

      int mult = 1;
      nxt = cin.peek();
      if (nxt >= '0' && nxt <= '9')
        mult = get_number();

      element e = findel(sym, pt, entries);
      if (e.atno == 0)
      { cout << "No element has symbol '" << sym << "'\n";
        bad = true;
        break; }

      molwt += e.atwt * mult; }

    if (! bad)
      cout << "Molecular weight " << molwt << "\n"; } }
\\