Bind and use variable

[mihaibudiu]

Is this illegal?

A(u) :- R(u, u).

It looks to me like this is just syntactic sugar for

A(u) :- R(u, v), u == v.

Maybe the compiler should accept this and make this transformation in the front-end.

[ryzhyk]

Is this illegal?

It is at the moment.

It looks to me like this is just syntactic sugar for
A(u) :- R(u, v), u == v.
Maybe the compiler should accept this and make this transformation in the front-end.

Yes, should be doable.

[mihaibudiu]

Here is another example which fails:

Rresult(_c, _p) :- Rprogress(strlen(_p), _c, _p).
Unknown variable: _p