eweda.installTo(this);

​

var Monad = function(type, defs) {

  for (name in defs){

    type.prototype[name] = defs[name];

  }

  return type;

};

function Left(value){

  this.value = value  

}

function Right(value){

  this.value=value;

}

​

Monad(Right, {

  bind:function(fn){

    return fn(this.value)

  }

})

​

Monad(Left, {

  bind: function(fn){

    return this;

  }

})

​

​

var land = eweda.curry(function(lr, n, pole){

    pole[lr] = pole[lr] + n;

    if(Math.abs(pole[0]-pole[1]) > 3) {

      return new Left("dead when land " + n + " became " + pole);

    } 

    return new Right(pole);

});

​

var landLeft = land(0)

var landRight = land(1);

​

var either = function(leftfn, rightfn, eth){

  if(eth.constructor.name === 'Left'){

    return leftfn(eth.value)

  }else if(eth.constructor.name === 'Right') {

    return rightfn(eth.value)

  }    

}

var stillAlive = function(x){

    console.log(x)

}

var dead = function(x){

    console.log('皮尔斯' + x);

}

// either(dead, stillAlive, landLeft(2, [0,0]));

​

var walkInLine = new Right([0,0]);

eitherDeadOrNot = walkInLine.bind(landLeft(2))

​

either(dead, stillAlive, eitherDeadOrNot)

​

​