Underline.js

window.print = function(s) { 
  document.write(s); 
}; 

window.puts = function(s) { 
  document.write(s); 
  document.write("<br>"); 
}; 

Array.prototype.equals = function(other) { 
  for(var i=0;i<this.length;i++) { 
    if(this[i] != other[i]) { 
      return false; 
    } 
  } 
  return true; 
}; 

Array.prototype.toString = function() { 
  var str = "["; 
  for(var i=0; i < this.length; i++) { 
    str += this[i].toString(); 
    if(i != (this.length-1)) { 
      str += ", "; 
    } 
  } 
  return str+"]"; 
}; 

Array.prototype.clone = function() { 
  var cloned = []; 
  for(var i=0;i<this.length;i++) { 
    cloned.push(this[i]) 
  } 
  return cloned; 
}; 

Array.prototype.each = function(fn) { 
  for(var i=0; i < this.length; i++) { 
    fn(this[i]); 
  } 
}; 

Array.prototype.map = function(fn) { 
  var mapped = []; 
  for(var i=0; i < this.length; i++) { 
    mapped.push(fn(this[i])); 
  } 
  return mapped; 
}; 

Array.prototype.reduce = function(fn) { 
  var ary = this.clone(); 
  while(true) { 
    if(ary.length == 0) { 
      return null; 
    } 
    if(ary.length == 1) { 
      return ary[0]; 
    } 
    var elem1 = ary.shift(); 
    var elem2 = ary.shift(); 
    ary.unshift(fn(elem1,elem2)); 
  } 
}; 

Array.prototype.select = function(fn) { 
  var selected = []; 
  for(var i=0; i < this.length; i++) { 
    if(fn(this[i])) { 
      selected.push(this[i]); 
    } 
  } 
  return selected; 
};