fogus · December 18, 2015 04:08
diff --git a/index.html b/index.html
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
  "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
  <title>a sketch</title>
  <script type="text/javascript" src="undermine.js"></script>
 </head>

 <body>
  <center>
    open the js console and play<br>
    <a href="http://www.functionaljavascript.com">more about these ideas</a>
  </center>
 </body>
 </html>
diff --git a/undermine.js b/undermine.js
 var exists = function(x) { return x != null; };
 var truthy = function(x) { return (x !== false) && exists(x); };

 var _filter = function(fun) {
  return function(coll) {
    var results = [];
    if (coll == null) return results;
    coll.forEach(function(value, index, list) {
      if (truthy(fun.call(null, value))) results.push(value);
    });
    return results;
  };
 };

 function filter(fun) {
  var coll = arguments[1];

  if (exists(coll)) return _filter(fun)(coll);
  
  return _filter(fun);
 }

 var _map = function(fun) {
  return function(coll) {
    var results = [];
    if (coll == null) return results;
    coll.forEach(function(value, index, list) {
      results.push(fun.call(null, value));
    });
    return results;
  };
 };

 function map(fun) {
  var coll = arguments[1];

  if (exists(coll)) return _map(fun)(coll);
  
  return _map(fun);
 }

 function double(n) { return 2*n; }

 /*

 map(double, [1,2,3])
 //=> [1, 4, 9]

 */

 var doubleAll = map(double);


 /*

 doubleAll([1,2,3]);
 //=> [1, 4, 9]

 */

 function greaterThan(l, r) {
  return l > r;
 }


 function schonfinkel(fun) {
  return function(first) {
    return function(last) {
      return fun(first, last);
    };
  };
 };

 function flip(fun) {
  return function() {
    return fun.call(null, arguments[1], arguments[0]);
  };
 }

 var gt = schonfinkel(flip(greaterThan));

 /*

 gt(5)
 //=> function(last) { ... }

 gt(5)(10000000);
 //=> true

 gt(5)(1);
 //=> false

 */

 var _reduce = function(fun, seed, coll) {
  var acc = seed;
  coll.forEach(function(value) {
    acc = fun.call(null, acc, value);
  });
  return acc;
 };

 function reduce(fun) {
  var count = arguments.length;
  var seed = arguments[1];
  var coll = arguments[2];
  var result;

  switch(count) {
  case 1:
    result = schonfinkel(_reduce.bind(null, fun));
    break;

  case 2:
    result = _reduce.bind(null, fun, seed);
    break;

  case 3:
    result = _reduce(fun, seed, coll);
    break;
  }

  return result;
 }

 function sum(x,y) { return x + y; }

 /*

 reduce(sum, 0, [1,2,3,4,5]);
 //=> 15

 */

 var summate = reduce(sum, 0);

 /*

 summate([1,2,3,4,5]);
 //=> 15

 */

 var pipeline = function(/*, funs */){
  var funs = Array.prototype.slice.call(arguments);

  return function(seed) {
    return reduce(function(l,r) { return r(l); },
                  seed,
                  funs);
  };
 };

 /*

 pipeline(double)(5);
 //=> 10

 */

 var tasks = pipeline(
  map(double)
  , filter(gt(5))
 );

 /*

 tasks([1,2,3,4,5]);
 //=> [6,8,10]

 */

 var moreTasks = pipeline(
  tasks
  , reduce(function(x,y) { return x*y }, 1)
 );

 /*

 moreTasks([1,2,3,4,5]);
 //=> 480

 */


 // more ideas like this at http://www.functionaljavascript.com/
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
	"http://www.w3.org/TR/html4/loose.dtd">
	<html>
	<head>
	<title>a sketch</title>
	<script type="text/javascript" src="undermine.js"></script>
	</head>

	<body>
	<center>
	open the js console and play<br>
	<a href="http://www.functionaljavascript.com">more about these ideas</a>
	</center>
	</body>
	</html>
	var exists = function(x) { return x != null; };
	var truthy = function(x) { return (x !== false) && exists(x); };

	var _filter = function(fun) {
	return function(coll) {
	var results = [];
	if (coll == null) return results;
	coll.forEach(function(value, index, list) {
	if (truthy(fun.call(null, value))) results.push(value);
	});
	return results;
	};
	};

	function filter(fun) {
	var coll = arguments[1];

	if (exists(coll)) return _filter(fun)(coll);

	return _filter(fun);
	}

	var _map = function(fun) {
	return function(coll) {
	var results = [];
	if (coll == null) return results;
	coll.forEach(function(value, index, list) {
	results.push(fun.call(null, value));
	});
	return results;
	};
	};

	function map(fun) {
	var coll = arguments[1];

	if (exists(coll)) return _map(fun)(coll);

	return _map(fun);
	}

	function double(n) { return 2*n; }

	/*

	map(double, [1,2,3])
	//=> [1, 4, 9]

	*/

	var doubleAll = map(double);


	/*

	doubleAll([1,2,3]);
	//=> [1, 4, 9]

	*/

	function greaterThan(l, r) {
	return l > r;
	}


	function schonfinkel(fun) {
	return function(first) {
	return function(last) {
	return fun(first, last);
	};
	};
	};

	function flip(fun) {
	return function() {
	return fun.call(null, arguments[1], arguments[0]);
	};
	}

	var gt = schonfinkel(flip(greaterThan));

	/*

	gt(5)
	//=> function(last) { ... }

	gt(5)(10000000);
	//=> true

	gt(5)(1);
	//=> false

	*/

	var _reduce = function(fun, seed, coll) {
	var acc = seed;
	coll.forEach(function(value) {
	acc = fun.call(null, acc, value);
	});
	return acc;
	};

	function reduce(fun) {
	var count = arguments.length;
	var seed = arguments[1];
	var coll = arguments[2];
	var result;

	switch(count) {
	case 1:
	result = schonfinkel(_reduce.bind(null, fun));
	break;

	case 2:
	result = _reduce.bind(null, fun, seed);
	break;

	case 3:
	result = _reduce(fun, seed, coll);
	break;
	}

	return result;
	}

	function sum(x,y) { return x + y; }

	/*

	reduce(sum, 0, [1,2,3,4,5]);
	//=> 15

	*/

	var summate = reduce(sum, 0);

	/*

	summate([1,2,3,4,5]);
	//=> 15

	*/

	var pipeline = function(/, funs /){
	var funs = Array.prototype.slice.call(arguments);

	return function(seed) {
	return reduce(function(l,r) { return r(l); },
	seed,
	funs);
	};
	};

	/*

	pipeline(double)(5);
	//=> 10

	*/

	var tasks = pipeline(
	map(double)
	, filter(gt(5))
	);

	/*

	tasks([1,2,3,4,5]);
	//=> [6,8,10]

	*/

	var moreTasks = pipeline(
	tasks
	, reduce(function(x,y) { return x*y }, 1)
	);

	/*

	moreTasks([1,2,3,4,5]);
	//=> 480

	*/


	// more ideas like this at http://www.functionaljavascript.com/