//<!--
 // Javascript scientific calculator  (4 March 1996)
 // (C) Copyright Rolf Howarth 1996
 // rolf@insect.demon.co.uk
 
 var NDIGITS = 16;
 var STACKSIZE = 12;
 
 var value = 0;        // current value in display
 var memory = GetCookie("CalcMemory");        // current value in memory
 if (!memory) memory = 0;
 var level = 0;        // no. of items on stack
 var entered = true;   // has value on display been 'entered'?
 var decimal = 0;              // multiplier when entering after decimal point
 var fixed = 0;        // force trailing zero display when entering decimals
 var exponent = false; // currently entering exponent?
 var inverse = false;  // has the INV key been pressed?
 
 if (location.search)
 {
        // pass in value through command line
        value = location.search.substring(1,location.search.length);
 }
 
 function stackItem()
 {
        this.value = 0;
        this.op = "";
 }
 
 function array(length)
 {
        this[0] = 0;
        for (i=0; i<length; ++i)
        {
               this[i] = 0;
               this[i] = new stackItem();
        }
        this.length = length;
 }
 
 stack = new array(STACKSIZE);
 
 function push(value,op,prec)
 {
        if (level==STACKSIZE)
               return false;
        for (i=level;i>0; --i)
        {
               stack[i].value = stack[i-1].value;
               stack[i].op = stack[i-1].op;
               stack[i].prec = stack[i-1].prec;
        }
        stack[0].value = value;
        stack[0].op = op;
        stack[0].prec = prec;
        ++level;
        return true;
}
 
function pop()
{
        if (level==0)
               return false;
        for (i=0;i<level; ++i)
        {
               stack[i].value = stack[i+1].value;
               stack[i].op = stack[i+1].op;
               stack[i].prec = stack[i+1].prec;
        }
        --level;
        return true;
 }
 
 function format(value)
 {
        var valStr = "" + value;
        if (valStr.indexOf("N")>=0 || (value == 2*value && value == 1+value))
               return "Error ";
        var i = valStr.indexOf("e")
        if (i>=0)
        {
               var expStr = valStr.substring(i+1,valStr.length);
               if (i>11) i=11;  // max 11 digits
               valStr = valStr.substring(0,i);
               if (valStr.indexOf(".")<0) valStr += ".";
               valStr += " " + expStr;
        }
        else
        {
               var valNeg = false;
               if (value < 0)
                       { value = -value; valNeg = true; }
 
               var valInt = Math.floor(value);
               var valFrac = value - valInt;
               var prec = NDIGITS - (""+valInt).length - 1;  // how many digits available after period
               if (! entered && fixed>0)
                       prec = fixed;
               var mult = " 1000000000000000000".substring(1,prec+2);
               var frac = Math.floor(valFrac * mult + 0.5);
 
               valInt = Math.floor(Math.floor(value * mult + .5) / mult);
 
               if (valNeg)
 
                       valStr = "-" + valInt;
 
               else
 
                       valStr = "" + valInt;
 
               var fracStr = "00000000000000"+frac;
               fracStr = fracStr.substring(fracStr.length-prec, fracStr.length);
               i = fracStr.length-1;
               if (entered || fixed==0)
               {
                       // remove trailing zeros unless fixed during entry.
                       while (i>=0 && fracStr.charAt(i)=="0")
                               --i;
                       fracStr = fracStr.substring(0,i+1);
               }
               if (i>=0) valStr += "." + fracStr;
//             document.result.debugField.value = "prec "+prec+", mult "+mult+", frac "+frac;
        }
        return valStr;
}
 
function refresh()
{
        var display = format(value);
        if (exponent)
        {
               if (expval<0)
                       display += " " + expval;
               else
                       display += " +" + expval;
        }
        if (display.indexOf(".")<0 && display != "Error ")
        {
               if (entered || decimal>0)
                       display += '.';
               else
                       display += ' ';
        }
        display = "               " + display;
        display = display.substring(display.length-NDIGITS-1,display.length);
        document.result.result.value = display;
        inverse = false;
}
 
function clearAll()
{
        level = 0;
        clear();
}
 
function clear()
{
        exponent = false;
        value = 0;
        enter();
        refresh();
}
 
function evalx()
{
        if (level==0)
               return false;
        op = stack[0].op;
        sval = stack[0].value;
//      alert("eval "+sval+op+value);
        if (op == "+")
               value = sval + value;
        else if (op == '-')
               value = sval - value;
        else if (op == '*')
               value = sval * value;
        else if (op == '/')
               value = sval / value;
        else if (op == 'pow')
               value = Math.pow(sval,value);
        pop();
        if (op=='(')
               return false;
        return true;
}
 
function openp()
{
        enter();
        if (!push(0,'(',0))
        {
               value = "NAN";
        }
        refresh();
}
 
function closep()
{
        enter();
        while (evalx())
               ;
        refresh();
}
 
function operator(op)
{
        enter();
        if (op=='+' || op=='-')
               prec = 1;
        else if (op=='*' || op=='/')
               prec = 2;
        else if (op=="pow")
               prec = 3;
        if (level>0 && prec <= stack[0].prec)
               evalx();
        if (!push(value,op,prec))
        {
               value = "NAN";
        }
        refresh();
 }
 
 function enter()
 {
        if (exponent)
               value = value * Math.exp(expval * Math.LN10);
        entered = true;
        exponent = false;
        decimal = 0;
        fixed = 0;
 }
 
 function equals()
 {
        enter()
        while (level>0)
               evalx();
        refresh();
}
 
function digit(n)
{
        if (entered)
        {
               value = 0;
               digits = 0;
               entered = false;
 
        }
 
        if (n==0 && digits==0)
 
        {
 
               refresh();
 
               return;
 
        }
 
        if (exponent)
        {
               if (expval<0)
                       n = -n;
               if (digits < 3)
               {
                       expval = expval * 10 + n;
                       ++digits;
                       refresh();
               }
               return;
        }
        if (value<0)
               n = -n;
        if (digits < NDIGITS-1)
        {
               ++digits;
               if (decimal>0)
               {
                       decimal = decimal * 10;
                       value = value + (n/decimal);
                       ++fixed;
               }
               else
                       value = value * 10 + n;
        }
        refresh();
}
 
function sign()
{
        if (exponent)
               expval = -expval;
        else
               value = -value;
        refresh();
}
 
function period()
{
        if (entered)
        {
               value = 0;
               digits = 1;
        }
        entered = false;
        if (decimal == 0)
        {
               decimal = 1;
        }
        refresh();
}
 
function exp()
{
        if (entered || exponent)
               return;
        exponent = true;
        expval = 0;
        digits = 0;
        decimal = 0;
        refresh();
}
 
function inv()
{
        inverse = !inverse;
}
 
function func(f)
{
        enter();
        if (f=="1/x")
               value = 1/value;
        else if (f=="swap")
        {
               var tmp = value;
               value = stack[0].value;
               stack[0].value = tmp;
        }
        else if (f=='n!')
        {
               if (value<0 || value>200 || value != Math.round(value))
                       value = "NAN";
               else
               {
                       var n = 1;
                       var i;
                       for (i=1;i<=value;++i)
                               n *= i;
                       value = n;
               }
        }
        else if (f=="MR")
               value = memory;
        else if (f=="M+")
        {
               memory += value;
               SetCookie("CalcMemory", memory);
        }
        else if (f=="Min")
        {
               memory = value;
               SetCookie("CalcMemory", memory);
        }
        else if (inverse)
        {
                if (f=="sin")
                       value = Math.asin(value)*180/Math.PI;
               else if (f=="cos")
                       value = Math.acos(value)*180/Math.PI;
               else if (f=="tan")
                       value = Math.atan(value)*180/Math.PI;
               else if (f=="log")
                       value = Math.exp(value * Math.LN10);
               else if (f=="log2")
                       value = Math.exp(value * Math.LN2);
               else if (f=="ln")
                       value = Math.exp(value);
               else if (f=="sqrt")
                       value = value*value;
               else if (f=="pi")
                       value = Math.E;
        }
        else
        {
                if (f=="sin")
                       value = Math.sin(value/180 * Math.PI);
               else if (f=="cos")
                       value = Math.cos(value/180 * Math.PI);
               else if (f=="tan")
                       value = Math.tan(value/180 * Math.PI);
               else if (f=="log")
                       value = Math.log(value)/Math.LN10;
               else if (f=="log2")
                       value = Math.log(value)/Math.LN2;
               else if (f=="ln")
                       value = Math.log(value);
               else if (f=="sqrt")
                       value = Math.sqrt(value);
               else if (f=="pi")
                       value = Math.PI;
        }
        refresh();
 }
 
 function hex()
 {
        //location = "hcalc.html?"+value;
 }
 
 /////////////
 //
 //  Cookie Functions - Second Helping  (21-Jan-96)
 //  Written by:  Bill Dortch, hIdaho Design <bdortch@netw.com>
//  The following functions are released to the public domain.
//
 
function getCookieVal (offset) {
  var endstr = document.cookie.indexOf (";", offset);
  if (endstr == -1)
    endstr = document.cookie.length;
  return unescape(document.cookie.substring(offset, endstr));
}
 
function GetCookie (name) {
  var arg = name + "=";
  var alen = arg.length;
  var clen = document.cookie.length;
  var i = 0;
  while (i < clen) {
     var j = i + alen;
     if (document.cookie.substring(i, j) == arg)
       return getCookieVal (j);
     i = document.cookie.indexOf(" ", i) + 1;
     if (i == 0) break; 
   }
   return null;
 }
 
 //  Function to create or update a cookie.
 //    name - String object object containing the cookie name.
 //    value - String object containing the cookie value.  May contain
 //      any valid string characters.
 //    [expires] - Date object containing the expiration data of the cookie.  If
 //      omitted or null, expires the cookie at the end of the current session.
 //    [path] - String object indicating the path for which the cookie is valid.
 //      If omitted or null, uses the path of the calling document.
 //    [domain] - String object indicating the domain for which the cookie is
 //      valid.  If omitted or null, uses the domain of the calling document.
 //    [secure] - Boolean (true/false) value indicating whether cookie transmission
 //      requires a secure channel (HTTPS).  
 //
 function SetCookie (name, value) {
   var argv = SetCookie.arguments;
   var argc = SetCookie.arguments.length;
   var expires = (argc > 2) ? argv[2] : null;
  var path = (argc > 3) ? argv[3] : null;
  var domain = (argc > 4) ? argv[4] : null;
  var secure = (argc > 5) ? argv[5] : false;
  document.cookie = name + "=" + escape (value) +
    ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) +
    ((path == null) ? "" : ("; path=" + path)) +
    ((domain == null) ? "" : ("; domain=" + domain)) +
    ((secure == true) ? "; secure" : "");
}
 
function DeleteCookie (name) {
  var exp = new Date();
  exp.setTime (exp.getTime() - 1);  // This cookie is history
  var cval = GetCookie (name);
  document.cookie = name + "=" + cval + "; expires=" + exp.toGMTString();
}
 
//
// End of cookie functions
//////////
 
// -->