Value Assignment Operator

Hi All,

I am trying to assign a variable the value of another variable - so I am
looking for something of the form X = Y, where X would have the value of
Y rather than checking if X is equal to Y or not. I saw something about
using :=, but this does not compile under both Sicstus Prolog and SWI
Prolog.

I look forward to hearing from you soon.

Regards,
George

On Apr 2, 1:08 pm, George <m...@me.com> wrote:
> Hi All,
>
> I am trying to assign a variable the value of another variable - so I am
> looking for something of the form X = Y, where X would have the value of
> Y rather than checking if X is equal to Y or not. I saw something about
> using :=, but this does not compile under both Sicstus Prolog and SWI
> Prolog.
>
> I look forward to hearing from you soon.
>
> Regards,
> George

Use is/2, for example X is 2+3.

regards, chip

On Apr 2, 1:08 pm, George <m...@me.com> wrote:
> Hi All,
>
> I am trying to assign a variable the value of another variable - so I am
> looking for something of the form X = Y, where X would have the value of
> Y rather than checking if X is equal to Y or not. I saw something about
> using :=, but this does not compile under both Sicstus Prolog and SWI
> Prolog.
>
> I look forward to hearing from you soon.
>
> Regards,
> George

Actually when you are dealing with variables X and Y,
the subgoal X=Y may have your desired effect.  Rather than
"assignment", the Prolog terminology would be to "unify"
these two variables.  So X=Y checks to see if these
expressions can be unified, and succeeds by effectively
treating them as thereafter bound to one another.

The "assignment" X=Y can fail only if X and Y are already
bound to expressions that cannot be unified.  Where you
may be frustrated is the fundamental design of Prolog in
not allowing reassigning values to a variable.  Once we
have succeeded in binding X = 2 and Y = 3, we cannot get
X = Y to succeed by "changing" the assignment of X.

regards, chip