The radix for Number is always 2. Providing this value simply future-proofs
against Decimal (should that ever happen). Then the programmer could say:
(x.radix == 10)? do_decimal_thing(x) : do_binary_thing(x)
instead of:
(typeof x == "decimal")? do_decimal_thing(x) : do_binary_thing(x)
I believe this would be nice if there is controversy over what "typeof
mydecimal" would be. Also it works for Objects which are numbers, when
typeof returns "object".
In my code I have
Number.prototype.radix = 2;
Number.prototype.numericType = "binary64";
which have proved rather useful.
Language purists may be offended by this engineer's nuts'n'bolts approach.
--------------------------------------------------
From: "Brendan Eich" <[email protected]>
Sent: Wednesday, March 21, 2012 7:00 AM
To: "Roger Andrews" <[email protected]>
Cc: <[email protected]>
Subject: Re: splitting Number into s-m-e, radix too (cf. DFP/Decimal)
Not gonna change number (the primitive type) to IEEE 754r DFP (not sure
you were getting at that in closing). Just FTR.
These Number.prototype getters can be implemented today in top browsers
(thanks to typed arrays) and in ES6 (binary data embraces and extends
typed arrays). See https://github.com/dherman/float.js/.
/be
Roger Andrews wrote:
Floating-point numbers are formed of a sign (s), significand (m),
exponent (e), and radix (b):
(-1)^s * m * b^e
where 0<=m<b.
Often we want to access the s-m-e values directly, especially the
significand. Notably when doing comparison for approximate equality by
"masking out" the rounding error in the low order bits; or some
multiprecise work. In ES5 this is painful.
The sign, significand, exponent, radix are intrinsic properties of a
Number (like the length of a String) - so how about exposing them as
properties of Number? Say the sign, significand, and exponent could be
read-write and the radix read-only.
Advantages:
1) extracting the significand is easy:
x.signif
2) scaling is easy (scaleB operation):
x.exponent += N
3) the logB operation is easy:
x.exponent
Also programmers could distinguish a binary value from a decimal without
using typeof, using the 'radix' property instead. This might
future-proof against the possible coming of a Decimal type without
breaking existing code. Does it help there?
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