// Do actually the computation
set<Assignment> SPGParser::computeReductible(int i, int j)
{
set<Assignment> as;
// Base case
if(i == j && isType(i))
{
if(isUnit(i))
as.insert(Assignment::singleton(headType[i]));
return as;
}
if(j == i+1)
{
if(isType(i) && isType(j) && gcon(i,j))
{
as.insert(Assignment::singleton(headType[i]));
// we could add j but headType[i] == headType[j] so it's no use
}
return as;
}
if(isType(i) && isType(j) &&
isStar(i+1) &&
isStar(j-1) &&
widx[j] == widx[i]+1 &&
gcon(i,j))
{
Assignment a = Assignment::singleton(headType[i]);
a.insert(headType[j]);
as.insert(a);
return as;
}
if(isType(i) && isType(j))
{
// A1a
for(int k = i+1; k < j-1; k++)
if(isType(k) && reductible(i,k) && reductible(k+1,j))
as = as + product(assignments[i][k], assignments[k+1][j]);
// A1b
for(int k = i+1; k < j-1; k++)
if(isRB(k) && isLB(k+1) && reductible(i,k) && reductible(k+1,j))
as = as + product(assignments[i][k], assignments[k+1][j]);
// A2
if(gcon(i,j) && reductible(i+1,j-1))
{
set<Assignment> a = assignments[i+1][j-1];
Assignment rhs;
rhs.insert(headType[i]);
rhs.insert(headType[j]);
set<Assignment> b;
b.insert(rhs);
as = as + product(a, b);
}
}
// A3a
if(isLB(i) && isType(j))
{
for(int k = i+1; k < j && widx[k] == widx[i]; k++)
if(isStar(k) && reductible(k+1, j))
as = as + assignments[k+1][j];
}
// A3b
if(isRB(j) && isType(i))
{
for(int k = j-1; k > i && widx[k] == widx[j]; k--)
if(isStar(k) && reductible(i,k-1))
as = as + assignments[i][k-1];
}
// A4a
if(isType(i) && isType(j) && isStar(i+1) && gcon(i,j)
&& widx[i] != widx[j])
{
for(int k = i+1; k < j && widx[k] == widx[i]; k++)
if(isLB(k+1) && reductible(k+1,j-1))
as = as + assignments[k+1][j-1];
}
// A4b
if(isType(i) && isType(j) && isStar(j-1) && gcon(i,j)
&& widx[i] != widx[j])
{
for(int k = j-1; k > i && widx[k] == widx[j]; k--)
if(isRB(k-1) && reductible(i+1,k-1))
as = as + assignments[i+1][k-1];
}
// A4c
if(isType(i) && isType(j) &&
isStar(i+1) && isStar(j-1) &&
1 + widx[i] < widx[j] &&
gcon(i,j))
{
int k1, k2;
for(k1 = i+1; k1 < j && !isRB(k1); k1++);
for(k2 = j-1; k2 > i && !isLB(k2); k2--);
if(reductible(k1,k2))
as = as + assignments[k1][k2];
}
// A5
if(isLB(i) && isRB(j))
{
float totalProb = 0;
for(int k1 = i+1; k1 < j && !isRB(k1); k1++)
{
if(isType(k1) && isStar(k1-1))
{
for(int k2 = j-2; k2 > i && !isLB(k2); k2--)
{
if(isType(k2) && isStar(k2+1) && reductible(k1,k2))
as = as + assignments[k1][k2];
}
}
}
}
return as;
}
//! Create a singleton
Assignment Assignment::singleton(int n)
{
Assignment a;
a.insert(n);
return a;
}