result_type operator() (logic::tag::xor_tag const& tag, result_type lhs, result_type rhs )
{
result_type out = { int(impl::new_var_id()) };
clause3( lhs, rhs,-out);
clause3( lhs,-rhs, out);
clause3(-lhs, rhs, out);
clause3(-lhs,-rhs,-out);
return out;
}
result_type operator() (logic::tag::ite_tag const& tag, result_type op1, result_type op2, result_type op3 )
{
result_type out = { int(impl::new_var_id()) };
clause3( op1, op3, -out);
clause3( op1,-op3, out);
clause3(-op1, op2, -out);
clause3(-op1,-op2, out);
return out;
}
void
encodeToCNF() {
#define clause2(a,b) \
({add_lit(a); add_lit(b); add_lit(0);})
#define clause3(a,b,c) \
({add_lit(a); add_lit(b); add_lit(c); add_lit(0);})
#define implies(a,b) clause2(-a, b);
#define implies_or(a,b,c) clause3(-a, b, c);
int f, d, l, t, e, c, r;
for (f = 0; f < S2; f++) {
clause3(white(f), black(f), nblack(f));
implies(white(f), -black(f));
implies(white(f), -nblack(f));
implies(nblack(f), -black(f));
implies(nblack(f), -white(f));
implies(black(f), -white(f));
implies(black(f), -nblack(f));
implies(white(f), numfield(f));
implies(nblack(f), xblack(f));
implies(nblack(f), numfield(f));
implies(black(f), xblack(f));
implies(white(f), -xblack(f));
implies(black(f), -numfield(f));
implies(xblack(f), -white(f));
implies(numfield(f), -black(f));
implies_or(numfield(f), white(f), nblack(f));
implies_or(xblack(f), black(f), nblack(f));
for (d = 0; d < S; d++) {
implies(num(f,d), numfield(f));
for (e = 0; e < S; e++) {
// each digit at most once in each row
t = same_row_but(f, e);
if (t != f)
implies(num(f, d), -num(t, d));
// each digit at most once in each column
t = same_col_but(f, e);
if (t != f)
implies(num(f, d), -num(t, d));
// only one digit at most in each cell
if (d != e)
implies(num(f, d), -num(f, e));
}
}
// numfield(f) => exists d . num(f,d)
add_lit(-numfield(f));
for (d = 0; d < S; d++)
add_lit(num(f, d));
add_lit(0);
// no single white fields
int c = field_col(f);
int r = field_row(f);
add_lit(-white(f));
if (c >= 1)
add_lit(-xblack(field(c-1, r)));
if (c < S-1)
add_lit(-xblack(field(c+1, r)));
if (r >= 1)
add_lit(-xblack(field(c, r-1)));
if (r < S-1)
add_lit(-xblack(field(c, r+1)));
add_lit(0);
}
// Encoding the straights:
// A constellation like B W W W B is a straight of len 3,
// when there are no blacks in between.
// The two B's can also be the border.
// Only straights of a length >= 2 are interesting.
// The implications are encoded into clauses like this:
// a&b => x
// -(a&b) | x
// -a | -b | x
for (f = 0; f < S2; f++) {
int col = field_col(f);
int row = field_row(f);
for (c = col+1; c < S; c++) {
// col is the first column
// c is the last column (inclusively)
int len = c-col+1;
if (col > 0)
add_lit(-xblack(same_row_but(f, col-1)));
if (c <= S-2)
add_lit(-xblack(same_row_but(f, c+1)));
for (int s = 0; s < len; s++)
add_lit(-white(same_row_but(f, col+s)));
add_lit(hstr(f, len));
add_lit(0);
if (col > 0)
implies(hstr(f,len), xblack(same_row_but(f, col-1)));
if (c <= S-2)
implies(hstr(f,len), xblack(same_row_but(f, c+1)));
for (int s = 0; s < len; s++)
implies(hstr(f,len), white(same_row_but(f, col+s)));
// hstr(f,len) => hstrd(f,len,0) | hstrd(f,len,1) ...
add_lit(-hstr(f, len));
int largest_mind = S-len;
for (int mind = 0; mind <= largest_mind; mind++)
add_lit(hstrd(f, len, mind));
add_lit(0);
// hstrd(f,len,d) => num(f,d) | num(f,d+1) ...
// for all the num()'s in the straight
for (int sc = col; sc <= c; sc++) {
int ff = same_row_but(f, sc);
for (int mind = 0; mind <= largest_mind; mind++) {
add_lit(-hstrd(f, len, mind));
for (int dig = 0; dig < len; dig++)
add_lit(num(ff, mind+dig));
add_lit(0);
}
}
}
for (r = row+1; r < S; r++) {
int len = r-row+1;
if (row > 0)
add_lit(-xblack(same_col_but(f, row-1)));
if (r <= S-2)
add_lit(-xblack(same_col_but(f, r+1)));
for (int s = 0; s < len; s++)
add_lit(-white(same_col_but(f, row+s)));
add_lit(vstr(f, len));
add_lit(0);
if (row > 0)
implies(vstr(f,len), xblack(same_col_but(f, row-1)));
if (r <= S-2)
implies(vstr(f,len), xblack(same_col_but(f, r+1)));
for (int s = 0; s < len; s++)
implies(vstr(f,len), white(same_col_but(f, row+s)));
// and the vstr(f,len) def
add_lit(-vstr(f, len));
int largest_mind = S-len;
for (int mind = 0; mind <= largest_mind; mind++)
add_lit(vstrd(f, len, mind));
add_lit(0);
// vstrd(f,len,d) => num(f,d) | num(f,d+1) ...
// for all the num()'s in the straight
for (int sc = row; sc <= r; sc++) {
int ff = same_col_but(f, sc);
for (int mind = 0; mind <= largest_mind; mind++) {
add_lit(-vstrd(f, len, mind));
for (int dig = 0; dig < len; dig++)
add_lit(num(ff, mind+dig));
add_lit(0);
}
}
}
}
printf("encoded into %i clauses\n", clausesptr);
}