CODEWITHSUNDEEP
prologclpfdsicstus-prolog
MartyIX
MartyIX

Reputation: 28666

How to define variables for the following scenario in CLPFD?

I have a set of variables T_1, T_2, ..., T_N and I would like to rewrite the following pseudocode in CLPFD: 

T_1 in 0..59, 
T_2 in 0..59, 
...
T_n in 0..59,

all_different([T_1, T_2, ..., T_n]),

FOREACH x in 0 to 59 do: 

   IF (x \in [T_1, T_2, T_3, ..., T_n]) THEN 
         Slot_x = 1 
   ELSE 
         Slot_x = 0

ENDFOREACH

How can I do that?

I would use count:

T_1 in 0..59, 
T_2 in 0..59, 
...
count(0, [T_1, T_2, ..., T_n], #=, Slot_0) % The number 0 can be at most once in the list
count(1, [T_1, T_2, ..., T_n], #=, Slot_1) % The number 1 can be at most once in the list
...

but I believe that a more experienced programmer would not write it this way.

Upvotes: 1

Views: 135

Answers (1)

Mats Carlsson
Mats Carlsson

Reputation: 1426

You can get rid of the all_different and count constraints as follows:

T_1 in 0..59, 
T_2 in 0..59, 
...
T_n in 0..59,

Slot_0 in 0..1,
Slot_1 in 0..1,
...
Slot_59 in 0..1,

global_cardinality([T_1, T_2, ..., T_n], [0-Slot_0, 1-Slot_1, ..., 59-Slot_59]).

Upvotes: 4

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