Lazy(object).length() ?

[ken-okabe]

To obtain object keys length with lazy.js, I do

var len = Lazy(object).keys().toArray().length;

However, I want to write simply

var len = Lazy(object).length();

Does this make sense? or any philosophy we should not have this?

Thx

[akre54]

For parity with underscore this would be size (which is basically implemented the way you described under the hood)

[ken-okabe]

Thannks akre54,

http://underscorejs.org/#size

Allright, so we can have size method both for Lazy Sequence and ObjectLikeSequence

I've notcied there is

 length GeneratedSequence#length

Returns the length of this sequence.
Signature

GeneratedSequence.length = function()

Name    Type(s)     Description
returns     number  

The length, or undefined if this is an indefinite sequence. 

and not sure what this is and how to use, also.

[dtao]

OK, I just added size so you can get the number of elements in any sequence.

Currently what I'm thinking is that size is offered for all sequence types (it's on the Sequence prototype) but may require full evaluation whereas length is only available on ArrayLikeSequences but does not require full (it is known up front, before iterating). Maybe this is confusing. I'm not sure I'm 100% settled on it yet. But I at least see the appeal of having a method that's available on all sequences, even if it potentially incurs a full evaluation (I've at least indicated as much in the docs for the method).

As for your question about GeneratedSequence#length: you get a generate sequence using Lazy.generate:

var sequence = Lazy.generate(Math.random, 10);

In the above example, sequence.length() will return 10, since a length of 10 was explicitly specified. On the other hand, you could also do this:

var sequence = Lazy.generate(Math.random);

In this case, sequence.length() will return undefined (although now that I think on it, maybe it should return Infinity) and can go on indefinitely. You would presumably pull from this sequence using, e.g., take:

sequence.take(10).toArray();

Alternately, a generated sequence could go on forever and let you just keep iterating asynchronously. This is how the prime number generator example works.

[dtao]

OK, this is now available in 0.3.1: http://danieltao.com/lazy.js/docs/#Sequence-size

[ken-okabe]

Thank you dtao.