The fact that you can't trivially do deep yields in callbacks is a good
thing.
For example
```
contents.split('\n').forEach(function(id) {
var info = yield
request.get('http://www.example.com?id='+id<http://www.example.com/?id='+id>,
resume);
});
```
Would have done N get request in series when you probably really want to do
something like
```
var infos = yield parallel(contents.split('\n').map(function (id) {
return request.get.bind(null, 'http://www.examples/com?id='+id)
}))
```
Which is yielding a single thing, where that single thing is do N get
requests in parallel.
If we make yielding too easy you will write sequential programs when you
really want to write parallel programs.
On Mon, Jul 15, 2013 at 12:11 AM, cpprototypes <[email protected]>wrote:
> Thanks for the replies, I have a better understanding now of how these
> libraries are using generators. I hope that one of these types of
> libraries becomes as popular as the async library and "standard" within the
> node community. This way of writing async code is much more elegant than
> the current way of using only callbacks and can help expand node.js usage
> into other areas. For instance, the script example I wrote is part of a
> larger command line script I was writing to test some services. Such
> scripting tends to follow a synchronous flow. I got really frustrated
> while writing it in an async way (since the natural flow is synchronous, it
> maps very poorly to the current callback-only style, even libraries like
> async don't help much). I eventually gave up and quickly wrote the script
> in python because I had to get the task done for the day. But I want
> node.js to eventually take python's place in my tool set. So I went back
> and tried it again with this new generators feature and it was going well
> until I ran into this issue. Some may say that such use is beyond the
> scope of node.js, but I think JS and node.js have potential to be more than
> just network async programming.
>
>
>
> On Friday, July 12, 2013 2:47:28 PM UTC-7, cpprototypes wrote:
>>
>> I'm using node 0.11.3 with --harmony-generators to try the new feature.
>> I found two libraries that should help use existing node callback-based
>> code with generators (suspend and galaxy). The code I'm trying to run was
>> similar to the following:
>>
>> (using suspend)
>>
>> var fs = require('fs');
>> var request = require('request');
>>
>> suspend(function* (resume) {
>> var contents = yield fs.readFile('idList.json', 'utf8', resume);
>> contents.split('\n').forEach(**function(id) {
>> var info = yield
>> request.get('http://www.**example.com?id='+id<http://www.example.com?id='+id>,
>> resume);
>> });
>> })();
>>
>> (using galaxy)
>>
>> var galaxy = require('galaxy');
>> var fs = galaxy.star(require('fs'));
>> var request = galaxy.star(require('request')**);
>>
>> function* main() {
>> var contents = yield fs.readFile('idList.json', 'utf8');
>> contents.split('\n').forEach(**function(id) {
>> var info = yield
>> request.get('http://www.**example.com?id='+id<http://www.example.com?id='+id>
>> );
>> });
>> };
>>
>> galaxy.unstar(main)(function(**err, result) {
>> console.log('done');
>> });
>>
>> Using either library, when node tries to execute the get request ("var
>> info = yield request.get...") it exits with the following error:
>>
>> SyntaxError: Unexpected identifier
>>
>> And the error highlights the "request" part in "var info = yield
>> request.get..." I'm guessing that the creation of the new function scope
>> in the forEach is somehow causing an issue. But I'm not sure why it's not
>> working.
>>
>>
>> --
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