Re: constraints order

[Daniel Diaz]

A FD solver is not complete. This means that you can "trust" the value 
of a variable only when you enumerate it (using for instance 
fd_labeling). In the case of your constraint and since you have not 
defined initial domains for X and Y the solver will will take a long 
time to try each value for X and to see there is no good value for Y.

Michel Levy wrote:
I do not understand why these two requests have different answers :
| ?- X #\=Y, X #=Y.
X = _#2(0..268435455)
Y = _#21(0..268435455)
| ?-  X #=Y, X #\= Y.
no.
This contradicts the assumption that the order of the constraints is 
unimportant.

Furthemore, in the official documentation, I read :
fd_all_different(List) constrains all variables in List to take distinct 
values. This is equivalent to posting an inequality constraint for each 
pair of variables.

But this equivalence is no true :
| ?- X #=Y, fd_all_different([X,Y]).
X = _#0(0..268435455)
Y = _#0(0..268435455)
yes
Can you explain me the difference ?

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