doitian/Readme.md

## Readme.md

      
    Raw
  

              Readme.md
            
          
    代码有点长，贴在gist了。
http://gist.github.com/430615#file_yield.js
主要思想就是把Enumerator里的程序分段存下来，然后手动控制执行。利用闭包保存状态。next()有负作用，懒得改了。

_s是一段不包含其它_开头函数的block.
_while, _if如字面
_yield 即yield

参数都需要函数。
run函数返回true时，表示yield了，这时next()返回。run返回false时，表示该段代码执行完毕。
其它语句如break, continue可以用类似方式加上。
灵感主要来自boost::lambda
好久没弄Javascript，不知道怎么样能去掉this前缀直接调用这些函数。

  
## yield.html
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>Test</title>
  </head>
  <body>
    <script type="text/javascript" src="yield.js">
    </script>
  </body>
</html>

## yield.js
function Class(obj) {
    var ctor = function () {
        if (obj.initialize) {
            obj.initialize.apply(this, arguments);
        }
    };
    ctor.prototype = obj;

    return ctor;
}

var WhileContext = Class({
    initialize: function(condition, sequence) {
        this.condition = condition;
        this.sequence = sequence;
    },

    run: function() {
        while (true) {
            if (!this.sequence.started()) {
                if (!this.condition()) {
                    return false;
                }
            }

            if (this.sequence.run()) {
                this.value = this.sequence.value;
                return true;
            }

            this.sequence.reset();
        }
    }
});

var IfContext = Class({
    initialize: function(condition, sequence) {
        this.condition = condition;
        this.sequence = sequence;
    },

    run: function() {
        if (!this.sequence.started() && !this.condition())
        {
            return false;
        }

        if (this.sequence.run()) {
            this.value = this.sequence.value;
            return true;
        }

        this.sequence.reset();
        return false;
    }
});

var StatementsContext = Class({
    initialize: function(proc) {
        this.proc = proc;
    },

    run: function() {
        this.proc();
        return false;
    }
});

var YieldContext = Class({
    initialize: function(proc) {
        this.proc = proc;
        this.should_yield = true;
    },

    run: function() {
        if (this.should_yield) {
            this.value = this.proc();
            this.should_yield = false;
            return true;
        }
        else {
            this.should_yield = true;
        }
    }
});

var SequenceContext = Class({
    initialize: function(proc) {
        this.context_list = [];
        proc.call(this);
        this.pc = -1;
    },

    run: function() {
        if (this.pc == -1) {
            this.pc = 0;
        }
        while (this.pc < this.context_list.length)
        {
            if (this.context_list[this.pc].run()) {
                this.value = this.context_list[this.pc].value;

                return true;
            }
            ++this.pc;
        }
        return false;
    },

    reset: function() {
        this.pc = -1;
    },

    started: function() {
        return this.pc >= 0;
    },

    _while: function(condition) {
        var context_list = this.context_list;
        return function (proc) {
            var sequence = new SequenceContext(proc);
            context_list.push(new WhileContext(condition, sequence));
        };
    },
    _if: function(condition) {
        var context_list = this.context_list;
        return function (proc) {
            var sequence = new SequenceContext(proc);
            context_list.push(new IfContext(condition, sequence));
        };
    },
    _yield: function(proc) {
        this.context_list.push(new YieldContext(proc));
    },
    _s: function(proc) {
        this.context_list.push(new StatementsContext(proc));
    }
});

var Enumerable = Class({
    initialize: function(proc) {
        this.sequence = new SequenceContext(proc);
        if (this.sequence.run()) {
            this.value = this.sequence.value;
            return this;
        }

        return null;
    },

    next: function() {
        if (this.sequence.run()) {
            this.value = this.sequence.value;
            return this;
        }

        return null;
    },

    takeWhile: function(condition) {
        var base = this;
        return new Enumerable(function() {
            this._if(function(){return condition(base.value)})(function (){
                this._yield(function(){return base.value});
                this._while(function(){return base.next() && condition(base.value)})(function (){
                    this._yield(function(){return base.value});
                });
            });
        });
    }
});

function main() {

    var oneTwoThree = new Enumerable(function(){
        this._yield(function() {return 1});
        this._yield(function() {return 2});
        this._yield(function() {return 3});
    });

    document.write("<h1>One Two Three</h1><ul>");
    for (; oneTwoThree; oneTwoThree = oneTwoThree.next()) {
        document.write("<li>" + oneTwoThree.value + "</li>");
    }
    document.write("</ul>\n");

    function Fib() {
        var i = 0;
        var j = 1;
        return new Enumerable(function(){
            this._while(function(){return true})(function(){
                this._yield(function(){return i});
                this._s(function(){
                    var next = i + j;
                    i = j;
                    j = next;
                });
            });
        });
    };

    var orig = new Fib();
    document.write("<h1>Fib take while < 100</h1><ul>");
    var fib = orig.takeWhile(function(e){return e < 100;});
    while (fib) {
        document.write("<li>" + fib.value + "</li>");
        fib = fib.next();
    }
    document.write("</ul>\n");
}

main();
	<?xml version="1.0" encoding="utf-8"?>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
	"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<title>Test</title>
	</head>
	<body>
	<script type="text/javascript" src="yield.js">
	</script>
	</body>
	</html>
	function Class(obj) {
	var ctor = function () {
	if (obj.initialize) {
	obj.initialize.apply(this, arguments);
	}
	};
	ctor.prototype = obj;

	return ctor;
	}

	var WhileContext = Class({
	initialize: function(condition, sequence) {
	this.condition = condition;
	this.sequence = sequence;
	},

	run: function() {
	while (true) {
	if (!this.sequence.started()) {
	if (!this.condition()) {
	return false;
	}
	}

	if (this.sequence.run()) {
	this.value = this.sequence.value;
	return true;
	}

	this.sequence.reset();
	}
	}
	});

	var IfContext = Class({
	initialize: function(condition, sequence) {
	this.condition = condition;
	this.sequence = sequence;
	},

	run: function() {
	if (!this.sequence.started() && !this.condition())
	{
	return false;
	}

	if (this.sequence.run()) {
	this.value = this.sequence.value;
	return true;
	}

	this.sequence.reset();
	return false;
	}
	});

	var StatementsContext = Class({
	initialize: function(proc) {
	this.proc = proc;
	},

	run: function() {
	this.proc();
	return false;
	}
	});

	var YieldContext = Class({
	initialize: function(proc) {
	this.proc = proc;
	this.should_yield = true;
	},

	run: function() {
	if (this.should_yield) {
	this.value = this.proc();
	this.should_yield = false;
	return true;
	}
	else {
	this.should_yield = true;
	}
	}
	});

	var SequenceContext = Class({
	initialize: function(proc) {
	this.context_list = [];
	proc.call(this);
	this.pc = -1;
	},

	run: function() {
	if (this.pc == -1) {
	this.pc = 0;
	}
	while (this.pc < this.context_list.length)
	{
	if (this.context_list[this.pc].run()) {
	this.value = this.context_list[this.pc].value;

	return true;
	}
	++this.pc;
	}
	return false;
	},

	reset: function() {
	this.pc = -1;
	},

	started: function() {
	return this.pc >= 0;
	},

	_while: function(condition) {
	var context_list = this.context_list;
	return function (proc) {
	var sequence = new SequenceContext(proc);
	context_list.push(new WhileContext(condition, sequence));
	};
	},
	_if: function(condition) {
	var context_list = this.context_list;
	return function (proc) {
	var sequence = new SequenceContext(proc);
	context_list.push(new IfContext(condition, sequence));
	};
	},
	_yield: function(proc) {
	this.context_list.push(new YieldContext(proc));
	},
	_s: function(proc) {
	this.context_list.push(new StatementsContext(proc));
	}
	});

	var Enumerable = Class({
	initialize: function(proc) {
	this.sequence = new SequenceContext(proc);
	if (this.sequence.run()) {
	this.value = this.sequence.value;
	return this;
	}

	return null;
	},

	next: function() {
	if (this.sequence.run()) {
	this.value = this.sequence.value;
	return this;
	}

	return null;
	},

	takeWhile: function(condition) {
	var base = this;
	return new Enumerable(function() {
	this._if(function(){return condition(base.value)})(function (){
	this._yield(function(){return base.value});
	this._while(function(){return base.next() && condition(base.value)})(function (){
	this._yield(function(){return base.value});
	});
	});
	});
	}
	});

	function main() {

	var oneTwoThree = new Enumerable(function(){
	this._yield(function() {return 1});
	this._yield(function() {return 2});
	this._yield(function() {return 3});
	});

	document.write("<h1>One Two Three</h1><ul>");
	for (; oneTwoThree; oneTwoThree = oneTwoThree.next()) {
	document.write("<li>" + oneTwoThree.value + "</li>");
	}
	document.write("</ul>\n");

	function Fib() {
	var i = 0;
	var j = 1;
	return new Enumerable(function(){
	this._while(function(){return true})(function(){
	this._yield(function(){return i});
	this._s(function(){
	var next = i + j;
	i = j;
	j = next;
	});
	});
	});
	};

	var orig = new Fib();
	document.write("<h1>Fib take while < 100</h1><ul>");
	var fib = orig.takeWhile(function(e){return e < 100;});
	while (fib) {
	document.write("<li>" + fib.value + "</li>");
	fib = fib.next();
	}
	document.write("</ul>\n");
	}

	main();