Hi Kashyap,
> I am having some trouble understanding the predicates and would really
> appreciate some explanation.
>
> /* Predicates */
> #define isNil(x) ((x)==Nil)
> #define isTxt(x) (num(x)&1)
> #define isNum(x) (num(x)&2)
> #define isSym(x) (num(x)&WORD)
> #define isSymb(x) ((num(x)&(WORD+2))==WORD)
> #define isCell(x) (!(num(x)&(2*WORD-1)))
This is miniPicoLisp, right? Only there we have isTxt().
> I can understand isTxt and isNum - bit 1 set means it's text and bit 2 set
> means its number.
Correct. As you know, this is depicted in miniPicoLisp/doc/structures
Primary data types:
num xxxxxx10
sym xxxxx100
pair xxxxx000
Raw data:
bin xxxxxxxx
txt xxxxxxx1
> However, why is WORD used for isSym? Could it not have
> been just 4 and why is does it have to be sizeof(long) - which is also 4 on
> 32bit
The reason is that miniPicoLisp compiles both on 32- and 64-bit architectures,
so sizeof(long) can be either 4 or 8. In that aspect it differs from the full
PicoLisp versions, which are always specialized for one architecture.
☺/ A!ex
--
UNSUBSCRIBE: mailto:[email protected]?subject=Unsubscribe
