[REBOL] Re: How to obtain a 64-bit IEEE754 representation of a decimal number
From: lmecir:mbox:vol:cz at: 2-Feb-2004 15:33
Hi Ashley,
>>convert: func [
>> x
>> /local y
>>] [
>> y: make struct! compose/deep [x [(type?/word x)]] reduce [x]
>> third y
>>]
>>
>>
>
>OK, this one has me stumpted. For us mere mortals, could you explain:
>
> >> help y
> Y is a struct of value: make struct! [x [decimal!]] [0.2]
> >> first y
> == [x [decimal!]]
> >> second y
> == [0.2]
> >> third y
> == #{9A9999999999C93F}
>
>how and why this works, in particular where "third y" comes from? Also,
>how does one reverse the conversion (i.e. get 0.2 from #{9A9999999999C93F}
>)?
>
This is a library interface, which is documented in:
http://www.rebol.com/docs/library.html
, where I found the informations needed to write the above function as
well as:
http://www.compkarori.com/vanilla/display/peek_and_poke.r
reverse-conversion: func [
x [binary!]
type [word!]
] [
y: make struct! compose/deep [x [(type)]] none
change third y x
y/x
]
Usage:
reverse-conversion #{9A9999999999C93F} 'decimal! ; == 0.2
>I assume this is another useful spinoff from the rounding project? ;)
>
Not exactly, it is mostly independent.
