internal error: missing builtin 'exists'

[jarble]

I tried to run this model in the MiniZinc playground using the Chuffed solver:

enum functions = {animal,dog};
type func = record(functions:funcs,int: input);
array[1..10] of var func:funcs;

function var bool:dog(int:t) =
(funcs:dog,input:t) in funcs;

var int:d1 = dog(1);

solve satisfy;

output [show(d1)];

But the solver shows this error message:

=====UNKNOWN=====
/usr/share/minizinc/std/stdlib/stdlib_array.mzn:266.3-32:
MiniZinc: evaluation error: internal error: missing builtin 'exists'
Process finished with non-zero exit code 1.

[cyderize]

As a workaround until this is fixed, you can pass the funcs array as an argument to your dog function:

function var bool:dog(array[int] of var func: fns, int:t) =
(funcs:dog,input:t) in fns;

var int:d1 = dog(funcs, 1);

[jarble]

@cyderize and @guidotack This error still appears in the MiniZinc playground. Has it not been updated to the latest version?

[Dekker1]

The problem is resolved when you select the “edge” version of MiniZinc in the playground. The fix has not been included in any release yet, so the “latest” version does not yet include the fix.

[jarble]

@Dekker1 Now a different error appears when running this model using the COIN-BC solver:

MiniZinc: flattening error: variable X_INTRODUCED_19_ needs finite bounds for linearisation. Or, use indicator constraints. Current domain is [[ [ -inf, 0 ] [ 1, 1 ] [ 2, inf ] ]]

Is this another compiler bug?

[cyderize]

I think this is just a limitation of how linearisation works for MIP solvers like CBC.

Without any bounds for the input field of the record, it's not possible to turn (funcs:dog,input:t) in funcs into an integer variable which the solver can handle.

You can add bounds with

type func = record(functions:funcs,-10..10: input);

which will fix the problem.