On Sat, 2020-07-25 at 13:35 +0200, Domingo Alvarez Duarte wrote:
> Hello !
>
> Trying to change the actual TUPLE structure by:
>
> ====
>
> #ifndef TUPLE_SIZE_T
> #define TUPLE_SIZE_T int
> #endif
> struct TUPLE
> {
> TUPLE_SIZE_T size;
> TUPLE_SIZE_T refcount;
> SYMBOL sym[1];
> /* symbol, which the component refers to; cannot be NULL */
> };
>
> ====
>
> I found the code bellow (in src/mpl/mpl3.c) that I'm not sure I
> understand it,
>
> it seems that it's only testing the last tuple against
> "code->arg.arg.y", shouldn't it be testing inside the loop for every
> tuple ?
>
> I would appreciate someone could help understand this code !
>
> ====
>
> int is_member(MPL *mpl, CODE *code, const TUPLE *tuple)
> { int value;
> ...
>
> case O_CROSS:
> { int j;
> value = is_member(mpl, code->arg.arg.x, tuple);
> if (value)
> { for (j = 1; j <= code->arg.arg.x->dim; j++)
> { xassert(tuple != NULL);
> tuple = tuple->next;
> }
> value = is_member(mpl, code->arg.arg.y, tuple);
> }
> }
> break;
>
> ====
>
> Cheers !
>
>
>
The routine is_member checks if the given n-tuple (specified by
'tuple') is a member of the given set (specified by 'code'). The check
is performed recursively by traversing the set expression tree. For
example, on evaluating the condition "... (x,y) in X cross Y ..." the
routine will check that x is in X and y is in Y.
