Number handling

Brendan Eich brendan at
Tue Oct 30 13:16:16 PDT 2007

On Oct 30, 2007, at 12:55 PM, Yehuda Katz wrote:

> After playing with the ES4 RI yesterday, my biggest concern comes  
> from the handling of various number types as compared to other types:
> * Literal numbers become ints, rather than Numbers. While ES4 is  
> still compatible with ES3 via some very strange use of the  
> constructor property, doing something like: var x:Number; x = 7;  
> throws an error.

As noted, an RI bug (apologies again). The ES4 proposal calls for  
interconversion among the types in AnyNumber.

> * ints are coercive by default. So function foo(x:int) { return  
> x }; foo(null) returns 0, while function foo(x:Number) { return  
> x }; foo(null) returns null. In effect function foo(x:int) { return  
> x } is identical to function foo(x:*) { return new int(x) }

More RI bugs. See

> * This is the same for all "primitives" like double.

When fixed (some of the problem has been fixed already), only for all  
members of AnyNumber. Current RI:

$ make repl
perl bin/
 >> var i:int = 3.14
 >> var j:double = 7
 >> var k:int = "moo"
[locn] builtins/
[stack] [init k()]
**ERROR** EvalError: uncaught exception: TypeError: incompatible  
types w/o conversion: val="moo" type=[ns public '__ES4__']::string   
wanted=[ns public '__ES4__']::int  (near builtins/
 >> var l:double = "oink"
[stack] [init k() | init l()]
**ERROR** EvalError: uncaught exception: TypeError: incompatible  
types w/o conversion: val="oink" type=[ns public '__ES4__']::string   
wanted=[ns public '__ES4__']::double  (near builtins/ 

> Of course, it's possible that some of this is just a failing in the  
> reference implementation, but looking through the available  
> materials leads me to believe that it's not *all* RI-related.

It is all RI-related, sorry again. The proposals and especially the  
overview are clearer about interconversion only among AnyNumber  
members. And ticket 113 is there to remind us.


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