Numerical operation order causes problems

[Joachim Jansen]

{ diag1(x,y) = x-(y+4). }

causes problems when { diag1(x,y) = (x-y)+4. diag2(x,y) = (x+y)-1. }

doesn't

Also, the resulting structure is not detected to be two-valued.

[Joachim Jansen]

Problems arise from faulty range generation.

Normal theory:

{ diag1(x,y) = x-y+3. }

{ diag2(x,y) = x+y-1. }

idpxsb_diag1(IDPXSB_x, IDPXSB_y, IDPXSB_var12) :- idpxsb_addr0x7fbad0150fb0(IDPXSB_x, IDPXSB_y, IDPXSB_var12), idpxsb_index(IDPXSB_x), idpxsb_index(IDPXSB_y), idpxsb_s15(IDPXSB_var12).

idpxsb_addr0x7fbad0150fb0(IDPXSB_x, IDPXSB_y, IDPXSB_var12) :- idpxsb_index(IDPXSB_x), idpxsb_index(IDPXSB_y), IDPXSB_var12 is IDPXSB_x-IDPXSB_y + 3.

idpxsb_s15(X) :- var(X), between(1,5,X).

idpxsb_s15(X) :- nonvar(X), X >= 1, X =< 5.

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Changing diag1's definition to: { diag1(x,y) = x-(y+3). } leads to generation of the following rules and ranges:

idpxsb_diag1(IDPXSB_x, IDPXSB_y, IDPXSB_var12) :- idpxsb_addr0x7fab101518a0(IDPXSB_x, IDPXSB_y, IDPXSB_var12), idpxsb_index(IDPXSB_x), idpxsb_index(IDPXSB_y), idpxsb_s51(IDPXSB_var12).

idpxsb_addr0x7fab101518a0(IDPXSB_x, IDPXSB_y, IDPXSB_var12) :- idpxsb_index(IDPXSB_x), idpxsb_index(IDPXSB_y), IDPXSB_var12 is IDPXSB_x - IDPXSB_y+3.

idpxsb_s51(X) :- var(X), between(-5,-1,X).

idpxsb_s51(X) :- nonvar(X), X >= -5, X =< -1.

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Manipulating diag2's definition in a similar fashing doesn't impact correctness.

[Joachim Jansen]

Please ignore the horrible arithmetics in this issue.

x-y+3 is not the same as x-(y+3)