fabioyamate/maybe.html

## maybe.html
<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>jQuery Snippet</title>
  </head>
  <body>
    <div id="container"></div>
    <script src="http://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.5.2/underscore-min.js"></script>
    <script src="http://cdnjs.cloudflare.com/ajax/libs/underscore-contrib/0.1.4/underscore-contrib.min.js"></script>
    <script>

function Just(value) {
  return {
    value: value,
    bind: function(f) {
      return f(this.value);
    },
    unit: Just
  };
}

function Nothing() { return Nothing; }

Nothing.bind = function() {
  return Nothing;
}

// liftM :: Monad m => (a1 -> r) -> m a1 -> m r
function liftM(f, m) {
  return m.bind(function(i) {
    return m.unit(f(i));
  });
}

// liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r
function liftM2(f, m1, m2) {
  return m1.bind(function(i) {
    return m2.bind(function(j) {
      return m1.unit(f(i, j));
    });
  });
}

// liftM3 :: Monad m => (a1 -> a2 -> a3 -> r) -> m a1 -> m a2 -> m a3 -> m r
function liftM3(f, m1, m2, m3) {
  return m1.bind(function(i) {
    return m2.bind(function(j) {
      return m3.bind(function(k) {
        return m1.unit(f(i, j, k));
      });
    });
  });
}

var phonebook = 1;
var governamentalDatabase = 2;
var taxDatabase = 3;

// lookup :: String -> ... -> Maybe
function lookup(name, database) {
  if (database == 1) {
    console.log('1');
    return Nothing;
  } else if (database == 2) {
    console.log('2');
    return Just('registration');
  } else if (database == 3) {
    console.log('3');
    return Just('number');
  }
}

function getTaxOwed(name) {
  return lookup(name, phonebook).bind(function(number) {
    return lookup(number, governamentalDatabase).bind(function(registration) {
      return lookup(registration, taxDatabase);
    });
  });
}

// getTaxOwed :: String -> Maybe
// do
//  number <- lookup(name, phonebook)
//  registration <- lookup(number, go...)
//  lookup(registration, taxDatab)
//  => Just(tax)


// lookup(name, phonebook) >>= \number
//      -> lookup(number, gover) >>= \registration
//                  ->  lookup(registration, taxDatabase)


// do
//   x <-Just(3)
//  y <- Just(4)
//  return $ x + y

console.log(getTaxOwed('fabio'));

function sum(a, b) {
  return a + b;
}

console.log(liftM2(sum, Just(3), Nothing));

function Try(expr) {
  try {
    return Success(expr);
  } catch(e) {
    return Failure(e);
  }
}

function Success(expr) {
  var value = expr();

  return {
    bind: function(f) {
      try {
        return f(value);
      } catch (e) {
        return Failure(e);
      }
    }
  };
}

function Failure(exception) {
  return {
    bind: function() {
      return exception;
    }
  };
}

parseNumber = function(v) {
  var value = parseInt(v, 10);

  if (value === NaN) {
    throw 'a';
  } else {
    return value;
  }
}

var a = Try(function() { return parseNumber("1") }).bind(function(a) {
  return Try(function() { return parseNumber("2") }).bind(function(b) {
    return Try(a + b);
  });
});

console.log(a);

    </script>
  </body>
</html>
	<!doctype html>
	<html lang="en">
	<head>
	<meta charset="utf-8">
	<title>jQuery Snippet</title>
	</head>
	<body>
	<div id="container"></div>
	<script src="http://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.5.2/underscore-min.js"></script>
	<script src="http://cdnjs.cloudflare.com/ajax/libs/underscore-contrib/0.1.4/underscore-contrib.min.js"></script>
	<script>

	function Just(value) {
	return {
	value: value,
	bind: function(f) {
	return f(this.value);
	},
	unit: Just
	};
	}

	function Nothing() { return Nothing; }

	Nothing.bind = function() {
	return Nothing;
	}

	// liftM :: Monad m => (a1 -> r) -> m a1 -> m r
	function liftM(f, m) {
	return m.bind(function(i) {
	return m.unit(f(i));
	});
	}

	// liftM2 :: Monad m => (a1 -> a2 -> r) -> m a1 -> m a2 -> m r
	function liftM2(f, m1, m2) {
	return m1.bind(function(i) {
	return m2.bind(function(j) {
	return m1.unit(f(i, j));
	});
	});
	}

	// liftM3 :: Monad m => (a1 -> a2 -> a3 -> r) -> m a1 -> m a2 -> m a3 -> m r
	function liftM3(f, m1, m2, m3) {
	return m1.bind(function(i) {
	return m2.bind(function(j) {
	return m3.bind(function(k) {
	return m1.unit(f(i, j, k));
	});
	});
	});
	}

	var phonebook = 1;
	var governamentalDatabase = 2;
	var taxDatabase = 3;

	// lookup :: String -> ... -> Maybe
	function lookup(name, database) {
	if (database == 1) {
	console.log('1');
	return Nothing;
	} else if (database == 2) {
	console.log('2');
	return Just('registration');
	} else if (database == 3) {
	console.log('3');
	return Just('number');
	}
	}

	function getTaxOwed(name) {
	return lookup(name, phonebook).bind(function(number) {
	return lookup(number, governamentalDatabase).bind(function(registration) {
	return lookup(registration, taxDatabase);
	});
	});
	}

	// getTaxOwed :: String -> Maybe
	// do
	// number <- lookup(name, phonebook)
	// registration <- lookup(number, go...)
	// lookup(registration, taxDatab)
	// => Just(tax)


	// lookup(name, phonebook) >>= \number
	// -> lookup(number, gover) >>= \registration
	// -> lookup(registration, taxDatabase)


	// do
	// x <-Just(3)
	// y <- Just(4)
	// return $ x + y

	console.log(getTaxOwed('fabio'));

	function sum(a, b) {
	return a + b;
	}

	console.log(liftM2(sum, Just(3), Nothing));

	function Try(expr) {
	try {
	return Success(expr);
	} catch(e) {
	return Failure(e);
	}
	}

	function Success(expr) {
	var value = expr();

	return {
	bind: function(f) {
	try {
	return f(value);
	} catch (e) {
	return Failure(e);
	}
	}
	};
	}

	function Failure(exception) {
	return {
	bind: function() {
	return exception;
	}
	};
	}

	parseNumber = function(v) {
	var value = parseInt(v, 10);

	if (value === NaN) {
	throw 'a';
	} else {
	return value;
	}
	}

	var a = Try(function() { return parseNumber("1") }).bind(function(a) {
	return Try(function() { return parseNumber("2") }).bind(function(b) {
	return Try(a + b);
	});
	});

	console.log(a);

	</script>
	</body>
	</html>