On Jul 11, 2013, at 9:01 PM, Luke Hoban wrote:

> Two questions on new Number APIs:
> 
> 1) Is it intentional that clz is on Number.prototype instead of Number?  Why?

Generally, operations that operate upon a value of a specific type are expressed as instance methods.  We see this all the time with regular objects but we also we see this in String where we have many methods that operate upon string values.  For Number we have the toFixed, etc. methods that convert  number values to strings.  To me, clz seem like it fall into this category of method that operate upon instances of a specific type.  For example, compare and contrast:

'00101000111100001111000011110000'.indexOf('1') // 2
0x28f0f0f0.clz()   //2

both use instance methods, applied to a primitive value, that  report something about the structure of the value

The (new) is* methods on the Number constructor are generally different in that they are predicates that test values that may not actually be numbers so they can't be Number.prototype methods.

I think there is a stronger case to me made for Math.clz(number).  Number.prototype and Math both seem like plausible homes for clz.  In the end, I placed it on Number prototype because it is an operation that is specific to a particular numeric encoding rather than an implementation of a general mathematical function. 

>  
> 2) Is it intentional that Number.toInteger(Infinity) returns true?
Huh? How's that?

Number.toInteger is specified as the single step:

    1 Return ToInteger(number)

and step 4 of the abstract operation ToInteger(number):

  4 If number is +0, -0, +∞, or -∞, return number.



> 
> Luke
> 
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>

On Jul 11, 2013, at 9:01 PM, Luke Hoban wrote:

> Two questions on new `Number` APIs:
> 
> 1) Is it intentional that `clz` is on `Number.prototype` instead of `Number`?  Why?

Generally, operations that operate upon a value of a specific type are expressed as instance methods.  We see this all the time with regular objects but we also we see this in `String` where we have many methods that operate upon string values.  For `Number` we have the `toFixed`, etc. methods that convert  number values to strings.  To me, `clz` seem like it fall into this category of method that operate upon instances of a specific type.  For example, compare and contrast:

```js
'00101000111100001111000011110000'.indexOf('1') // 2
0x28f0f0f0.clz()   //2
```

both use instance methods, applied to a primitive value, that  report something about the structure of the value

The (new) `is*` methods on the `Number` constructor are generally different in that they are predicates that test values that may not actually be numbers so they can't be `Number.prototype` methods.

I think there is a stronger case to me made for `Math.clz(number)`.  `Number.prototype` and `Math` both seem like plausible homes for `clz`.  In the end, I placed it on `Number` prototype because it is an operation that is specific to a particular numeric encoding rather than an implementation of a general mathematical function. 

> 2) Is it intentional that `Number.toInteger(Infinity)` returns `true`?

Huh? How's that?

`Number.toInteger` is specified as the single step:

> 1 Return ToInteger(number)

and step 4 of the abstract operation ToInteger(number):

> 4 If number is +0, -0, +∞, or -∞, return number.