A chainable calculator

equation.js

// A chainable little calculator thingy.

var equation = {
  i:0,
  _int:function(x){
    return parseInt(x,10);
  },
  set:function(x){
   this.i = this._int(x);
   return this;
  },
  plus:function(x){
   this.i+=this._int(x);
   return this;
  },
  minus:function(x){
   this.i-=this._int(x);
   return this;
  },
  times:function(x){
   this.i*=this._int(x);
   return this;
  },
  dividedBy:function(x){
   x=this._int(x);
   if (x===0) {
     this.error('Division by zero is not possible');}
   else if (this.i === 0) {
     this.i = 0;
   }
   else {
     this.i/=x;
   }
   return this;
  },
  error:function(msg){
    this.i = msg;
  },
  toString:function(){
    return this.i;
  }
};


// an example equation. note that the order of operations is serial
var c = equation.set(5).plus(5).times(10).dividedBy(25).times(100).dividedBy(2); // 200
window.alert(c);